WO2016038079A1

WO2016038079A1 - Plants with altered fruit abscission properties

Info

Publication number: WO2016038079A1
Application number: PCT/EP2015/070589
Authority: WO
Inventors: Benjamin Laga; Mieke STEVENS
Original assignee: Bayer Cropscience Nv
Priority date: 2014-09-11
Filing date: 2015-09-09
Publication date: 2016-03-17

Abstract

The present invention relates to plants having increased pod drop resistance. More specifically, the invention relates to Brassica plants in which expression of PGAZ is functionally reduced. Provided are Brassica plants comprising mutant PGAZ alleles, and Brassica plants in which expression of PGAZ is reduced. Also provided are methods and means to produce Brassica plants with increased pod drop resistance.

Description

PLANTS WITH ALTERED FRUIT ABSCISSION PROPERTIES

FIELD OF THE INVENTION

[1] This invention relates to crop plants and parts, particularly Brassica plants, with increased yield, more specifically with increased pod drop resistance. The invention also relates to nucleic acids encoding abscission-related polyalacturonases (PGAZ), and mutants thereof, that affect pod drop resistance in plants. Methods are also provided to identify molecular markers associated with reduced pod drop resistance.

BACKGROUND OF THE INVENTION

[2] Pod shedding, or pod drop, can have a major impact on seed yield in oilseed crops (Gan et al., 2008, Can J Plant Sci 88:267; Cavalieri et al., 2014, Crop Science 54: 1184). Pod drop is caused by the abscission of undehisced siliques at the pedicel.

[3] Shedding of plant organs, such as pods, takes place at predetermined positions called abscission zones. Genes contributing to cell wall abscission are β- 1 ,4-glucanases, abscission-related

polygalacturonases (PGAZ), and expansins. (Roberts et al., 2002, Annu Rev Plant Biol 53:131).

[4] Basu et al., 2013, Plant Physiol 162:96, describe that enhancement of levels of indoleacetic acid (IAA) specifically in the abscission zone, results in delay of organ loss. When the gain- of- function AXR3-1 gene was transactivated in order to disrupt auxin signalling, flowers failed to shed their sepals, petals and anthers during pod expansion and maturity, and these organs frequently remained attached to the plant.

[5] Wei et al (2010, Plant Physiology 153:1031) report on a member of the DOF transcription factor family DOF4.7 is expressed robustly in the abscission zone. Constitutive expression of DOF4.7 results in an ethylene-independent floral organ abscission deficiency. DOF4.7 has binding activity to cis- elements in the promoter of PGAZ, and is presumed to regulate abscission by regulation of expression of cell wall hydrolysis enzymes.

[6] Gonzalez-Carranza et al., 2002, Plant Physiol 128:534, identified a gene encoding a polygalacturonase (PG) from Brassica napus and identified its ortholog (At2g41850) in Arabidopsis. this abscission-related polygalacturonase (PGAZ) is expressed specifically at the base of cauline leaves, anther filaments, petals, and sepals at the time of shedding, and, more specifically, in the abscission zone, and at the site of lateral root emergence. A T-DNA insertion line of this gene in Arabidopsis exhibited delayed floral organ shedding (Gonzalez-Carranza et al., 2007., J Exp Bot 58:3719). Kim and Patterson (2006, Plant Signaling and Behavior 1 :6: 281) identified four floral organ abscission specific - - polygalacturonases in Arabidopsis: At2g41850, At2g43880, At2g43890, and At3g07970. A T-DNA insertion line for At2g41850 showed slight delay in floral organ abscission.

[7] Abscission of the fruit, such as siliques or pods, takes place at the abscission zone of the pedicel. Genes known to be expressed in pedicel abscission zones are the glycoside hydrolases GISH9B 1 , SIGH9B2 and SIGH9B4 in tomato, the glycoside hydrolases TAPG1, TAPG2, TAPG4 in tomato, and the Expansin AtWXPIO in vestigial pedicel abscission zones of Arabidopsis (i.e. abscission zones of pedicels which do not normally undergo abscission). (Estornell et al., (2013) Plant Sci 199-200:48). Tomato plants with a JOINTLESS mutation fail to develop abscission zones on their pedicels, and abscission of flowers or fruit does not occur normally. JOINTLESS has been identified as a MADS box gene (Mao et al., (2000), Nature 406:910).

[8] Knowledge on genes expressed in the abscission zone of the pedicel of pods or siliques is limited. Therefore, a need remains to identify genes of which modulation of expression affects abscission of pods or siliques.

SUMMARY OF THE INVENTION [9] The inventors have found that pod drop resistance in Brassica plants can be controlled by controlling the number and/or types of PGAZ genes/alleles that are "functionally expressed" in said plants, i.e. that result in functional (biologically active) PGAZ protein. By combining certain mutant alleles of the PGAZ genes, resulting in a reduction of the level of functional PGAZ protein, the pod drop resistance can be significantly increased. It was found that the more mutant PGAZ alleles are combined in a plant, the greater is the increase in pod drop resistance.

[10] Thus, in a first aspect, a Brassica plant is provided comprising at least two PGAZ genes, characterised in that it comprises at least one mutant PGAZ allele in its genome. In a further aspect, said mutant PGAZ allele is a mutant allele of a PGAZ gene comprising a nucleic acid sequence selected from the group consisting of:

- a nucleotide sequence which comprises at least 90% sequence identity to SEQ ID NO: 1,

SEQ ID NO: 4, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 13, SEQ ID NO: 16, SEQ ID NO: 19, SEQ ID NO: 22, SEQ ID NO: 25, SEQ ID NO: 28, SEQ ID NO: 31, SEQ ID NO: 34, SEQ ID NO: 37, SEQ ID NO: 40, or SEQ ID NO: 43;

a nucleotide sequence comprising a coding sequence which comprises at least 90% sequence identity to SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 8, SEQ ID NO: 11, SEQ ID NO: 14, SEQ ID NO: 17, SEQ ID NO: 20, SEQ ID NO: 23, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 32, SEQ ID NO: 35, SEQ ID NO: 38, SEQ ID NO: 41, or SEQ ID NO: 44; and a nucleotide sequence encoding an amino acid sequence which comprises at least 90%> sequence identity to SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 12, SEQ

ID NO: 15, SEQ ID NO: 18, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 27, SEQ ID NO: 30, SEQ ID NO: 33, SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, or SEQ ID NO: 45.

[11] In a further aspect, the plant according to the invention is a Brassica plant comprising four PGAZ genes, said Brassica plant selected from the group consisting of Brassica napus, Brassica juncea and Brassica carinata. In another embodiment, the plant according to the invention comprises comprising at least two mutant PGAZ alleles, or at least three mutant PGAZ alleles, or at least four mutant PGAZ alleles, or at least five mutant PGAZ alleles, or at least six mutant PGAZ alleles, or at least seven mutant PGAZ alleles, or at least eight mutant PGAZ alleles.

[12] In yet another embodiment, the plants according to the invention comprise a mutant PGAZ allele selected from the group consisting of:

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2422 of SEQ ID NO: 4;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2140 of SEQ ID NO: 4;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2212 of SEQ ID NO: 4;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3356 of SEQ ID NO: 7;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3531 of SEQ ID NO: 7;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3245 of SEQ ID NO: 7;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3275 of SEQ ID NO: 7;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2361 of SEQ ID NO: 10;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2442 of SEQ ID NO: 10;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2464 of SEQ ID NO: 13;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2473 of SEQ ID NO: 13.

[13] In again a further embodiment, said plant is homozygous for the mutant PGAZ allele. In yet another embodiment, said plant has increased pod drop resistance. A further embodiment provides a plant cell, pod, seed or progeny of the plant according to the invention. [14] In yet another aspect of the invention, a Brassica plant is provided comprising at least two PGAZ genes, said plant comprising an RNA molecule inhibitory to at least one PGAZ gene.

[15] In another embodiment, the plants according to the invention have increased pod drop resistance. In another aspect, a plant cell, pod, seed, or progeny of the plant according to the invention is provided.

[16] In another aspect of the invention, a mutant allele of a Brassica PGAZ gene is provided, wherein the PGAZ gene is selected from the group consisting of:

a nucleotide sequence which comprises at least 90% sequence identity to SEQ ID NO: 1, SEQ ID NO: 4, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 13, SEQ ID NO: 16, SEQ ID NO: 19, SEQ ID NO: 22, SEQ ID NO: 25, SEQ ID NO: 28, SEQ ID NO: 31, SEQ ID NO:

34, SEQ ID NO: 37, SEQ ID NO: 40, or SEQ ID NO: 43;

a nucleotide sequence comprising a coding sequence which comprises at least 90% sequence identity to SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 8, SEQ ID NO: 11, SEQ ID NO: 14, SEQ ID NO: 17, SEQ ID NO: 20, SEQ ID NO: 23, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 32, SEQ ID NO: 35, SEQ ID NO: 38, SEQ ID NO: 41, or SEQ ID NO: 44; and a nucleotide sequence encoding an amino acid sequence which comprises at least 90%> sequence identity to SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 12, SEQ ID NO: 15, SEQ ID NO: 18, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 27, SEQ ID NO: 30, SEQ ID NO: 33, SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, or SEQ ID NO: 45.

[17] In another embodiment, said mutant allele is selected from the group consisting of:

- a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 3531 of SEQ ID NO: 7;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3275 of SEQ ID NO: 7; a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2361 of SEQ ID NO: 10;

[18] Yet another embodiment provides a chimeric gene comprising the following operably linked DNA fragments: (a) a plant-expressible promoter; (b) a DNA region, which when transcribed yields an RNA or protein molecule inhibitory to one or more PGAZ genes; and, optionally (c) a 3' end region involved in transcription termination and polyadenylation.

[19] Another embodiment provides a method for identifying a mutant PGAZ allele according to the invention in a biological sample, said method comprising determining the presence of a mutant PGAZ specific region in a nucleic acid present in said biological sample.

[20] It is another aspect of the invention to provide a method for determining the zygosity status of a mutant PGAZ allele according to the invention in a Brassica plant, plant material or seed, which comprises determining the presence of a mutant and/or a corresponding wild type PGAZ specific region in the genomic DNA of said plant, plant material or seed.

[21] Yet another embodiment provides a kit for identifying a mutant PGAZ allele according to the invention, in a biological sample, comprising a set of at least two primers, said set being selected from the group consisting of:

a set of primers, wherein one of said primers specifically recognizes the 5' or 3' flanking region of the mutant PGAZ allele and the other of said primers specifically recognizes the mutation region of the mutant PGAZ allele, and

a set of primers, wherein one of said primers specifically recognizes the 5' or 3' flanking region of the mutant PGAZ allele and the other of said primers specifically recognizes the joining region between the 3' or 5' flanking region and the mutation region of the mutant PGAZ allele, respectively;

or said kit comprising a set of at one probe, said probe being selected from the group consisting of:

a probe specifically recognizing the mutation region of the mutant PGAZ allele, and a probe specifically recognizing the joining region between the 3' or 5' flanking region between the mutation region of the mutant PGAZ allele. [22] In yet a further embodiment, a method is provided for transferring at least one selected mutant PGAZ allele according to the invention, from one plant to another plant comprising the steps of: (a) identifying a first plant comprising at least one selected mutant PGAZ allele using the method according to the invention, (b) crossing the first plant with a second plant not comprising the at least one selected mutant PGAZ allele and collecting Fl hybrid seeds from said cross, (c) optionally, identifying Fl plants comprising the at least one selected mutant PGAZ allele using the method according to the invention, (d) backcrossing the Fl plants comprising the at least one selected mutant PGAZ allele with the second plant not comprising the at least one selected mutant PGAZ allele for at least one generation (x) andcollecting BCx seeds from said crosses, and (e) identifying in every generation BCx plants comprising the at least one selected mutant PGAZ allele using the method according to the method of the invention.

[23] Also provided is a method to increase pod drop resistance, comprising introducing at least one mutant PGAZ allele into a Brassica plant, or comprising introducing the chimeric gene according to the invention into a Brassica plant. [24] Also provided is a method for production of seeds, said method comprising sowing the seeds according to the invention, growing plants from said seeds, and harvesting seeds from said plants.

[25] In again another embodiment, a Brassica plant is provided selected from the group consisting of (a) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2422 of SEQ ID NO: 4 and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2361 of SEQ ID NO: 10, reference seeds comprising said allele having been deposited at the NCIMB Limited on 3 July 2014, under accession number NCIMB 42263; (b) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2212 of SEQ ID NO: 4, and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2361 of SEQ ID NO: 10, reference seeds comprising said allele having been deposited at the NCIMB Limited on 3 July 2014, under accession number NCIMB 42264, (c) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3356 of SEQ ID NO: 7 and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2473 of SEQ ID NO: 13, reference seeds comprising said allele having been deposited at the NCIMB Limited on 3 July 2014, under accession number NCIMB 42265; and (d) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3275 of SEQ ID NO: 7 and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2473 of SEQ ID NO: 13, reference seeds comprising said alleles having been deposited at the NCIMB Limited on 3 July 2014, under accession number NCIMB 42266. _Η

[26] Further provided is the use of the mutant PGAZ alleles according to the invention or the chimeric gene according to the invention to increase pod drop resistance, and the use of the plants or the seeds according to the invention to produce oilseed rape oil or an oilseed rape seed cake.

[27] It is another aspect of the invention to provide a method for producing food or feed, such as oil, meal, grain, starch, flour or protein, or an industrial product, such as biofuel, industrial chemicals, a pharmaceutical or a nutraceutical, said method comprising (a) obtaining the plant or a part thereof or the seeds according to the invention, and (b) preparing the food, feed or industrial product from the plant or part thereof.

BRIEF DESCRIPTION OF THE DRAWINGS [28] Figure 1 : In silico expression analysis of the four PGAZ genes PGAZ-A1 (diamonds), PGAZ- Cl (squares), PGAZ-A2 (triangles) and PGAZ-C2 (crosses) in different tissues: roots of 2 weeks old plants (1); Cotyledons 10 days after sowing (DAS) (2); stems 15 DAS (3); stems 33 DAS (4); young leaf 33 DAS (5); apical meristem + smallest leaf, 33 DAS (6); small flower bud 42 DAS (7); big flower bud 42 DAS > 5 mm (8); open flower 52 DAS (9); pod, 14-20 days after flowering (DAF) (10); pod 21-25 DAF (11); seeds 14-20 DAF (12); seeds 21-25 DAF (13); seeds 26-30 DAF (14); seeds 31-35 DAF (15); seeds 42 DAF (16); seeds 49 DAF (17). Expression values are in normalized counts per million (cpm).

[29] Figure 2: Relative PGAZ expression (in percentages) in B. napus in pod-pedicel dehiscence zone (P) compared to leaf dehiscence zone (L).

[30] Figure 3: Force (Fg) in grams required to remove pods from double mutant plants for different PGAZ genes grown in the greenhouse. - represents wild-type alleles, whereas Al, A2, CI and C2 represent the mutant alleles. I: Al : PGAZ-A1-EMS03; CI : PGAZ-Cl-EMSOl ; II: Al : PGAZ-A1 -EMS- 05, CI : PGAZ-C1-EMS01 ; III: A2: PGAZ-A2-EMS06; CI : PGAZ-C1-EMS01 ; IV: A2: PGAZ-A2- EMS11 ; CI : PGAZ-C1-EMS01 ; V: A2: PGAZ-A2-EMS06; C2: PGAZ-C2-EMS 13 ; VI: A2: PGAZ-A2- EMS11 ; C2: PGAZ-C2-EMS 13. A: F1 S1 non BC generation; B: BC1 S1 generation. [31] Figure 4: Force (Fg) in grams required to remove pods from quadruple mutant plants for different PGAZ genes grown in the greenhouse. WT: wild-type control. - represents wild-type alleles, whereas Al, A2, CI and C2 represent the mutant alleles Plants were of the BC1 S1 generation.—/—/—/— is the wild-type segregant, whereas the wild-type control is a control line without the PGAZ mutations. A: PGAZ- Al -EMS03/PGAZ- A2-EMS06/PGAZ-C 1 -EMS01 /PGAZ-C2-EMS 13 mutant alleles; B: PGAZ- Al -EMS05/PGAZ- A2-EMS 11 /PGAZ-C 1 -EMS01 /PGAZ-C2-EMS 13.

[32] Figure 5: Alignment of PGAZ amino acid sequences of SEQ ID NOs: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, and 45. Boxes indicate the conserved motifs. GENERAL DEFINITIONS

[33] "Pod drop" as used herein refers to the abscission of the siliques or pods from the plants.

Abscission may, but does not need to occur at the abscission zone of the pedicel.

[34] "Increased pod drop resistance" as used herein, refers to an increased resistance of the pods to dehisce from the plants, and thus to decreased pod drop. The level of pod drop resistance is positively correlated with the strength of adherence of the pods to the plants. Increased pod drop resistance can also be expressed as increased retention force of the pods. A measure for pod drop resistance is therefore the force required for pod detachment from the plants. The force required for detachment of the pods from the plants can be measured as described herein in the Examples. Increased pod drop resistance results in an increased number of pods remaining attached to the plants at harvest. Increased pod drop resistance therewith can increase the seed yield. Increased pod drop resistance can be an increase with at least 5%, or at least 10%, or at least 15%, or at least 20%, or at least 30%, or at least 40%, or at least 60%, or at least 80%, or at least 100%, or at least 120%, or at least 150%, or at least 180%, or at least 200%,of the force required for detachment of the pods from the plants. [35] A Brassica "fruit", as used herein, refers to an organ of a Brassica plant that develops from a gynoecium composed of fused carpels, which, upon fertilization, grows to become a "(seed) pod" or "silique" that contains the developing seeds. A Brassica "(seed) pod" or "silique" consists of a fruit wall (carpel) enclosing two locules separated by the septum. The "dehiscence zones" develop at the carpel margins adjacent to the septum and run the length of the silique. The cells of the dehiscence zone eventually begin to degrade and this weakens the contact between the carpel walls or valves and the septum. The loss of cellular cohesion is confined to the cells of the dehiscence zone and results from middle lamella breakdown (Meakin and Roberts, 1990, J Exp Bot 41, 995-1011).

[36] "Abscission zone", as used herein, refers to tiers of small, densely cytoplasmic cells located at sites of organ detachment. Within abscission zones, one or more cell layers reside that separate in response to developmental or enviranmetnal cues (Cai and Lashbrook (2008) Plant Physiol 146:1305).

[37] "Crop plant" refers to plant species cultivated as a crop, such as Brassica napus (AACC, 2n=38), Brassica juncea (AABB, 2n=36), Brassica carinata (BBCC, 2n=34), Brassica rapa (syn. B. campestris) (AA, 2n=20), Brassica oleracea (CC, 2n=18) or Brassica nigra (BB, 2n=16). The definition does not encompass weeds, such as Arabidopsis thaliana. [38] A "Brassica plant" as used herein refers to allotetraploid or amphidiploid Brassica napus (AACC, 2n=38), Brassica juncea (AABB, 2n=36), Brassica carinata (BBCC, 2n=34), or to diploid Brassica rapa (syn. B. campestris) (AA, 2n=20), Brassica oleracea (CC, 2n=18) or Brassica nigra (BB, 2n=16). [39] A "Crop of oilseed rape" as used herein refers to oilseed rape cultivated as a crop, such as Brassica napus, Brassica juncea, Brassica carinata, Brassica rapa (syn. B. campestris), Brassica oleracea or Brassica nigra.

[40] The term "nucleic acid sequence" (or nucleic acid molecule) refers to a DNA or RNA molecule in single or double stranded form, particularly a DNA encoding a protein or protein fragment according to the invention. An "endogenous nucleic acid sequence" refers to a nucleic acid sequence within a plant cell, e.g. an endogenous allele of a PGAZ gene present within the nuclear genome of a Brassica cell. An "isolated nucleic acid sequence" is used to refer to a nucleic acid sequence that is no longer in its natural environment, for example in vitro or in a recombinant bacterial or plant host cell. [41] The term "gene" means a DNA sequence comprising a region (transcribed region), which is transcribed into an RNA molecule (e.g. into a pre-mRNA, comprising intron sequences, which is then spliced into a mature mRNA, or directly into a mRNA without intron sequences) in a cell, operable linked to regulatory regions (e.g. a promoter). A gene may thus comprise several operably linked sequences, such as a promoter, a 5' leader sequence comprising e.g. sequences involved in translation initiation, a (protein) coding region (cDNA or genomic DNA) and a 3 ' non-translated sequence comprising e.g. transcription termination sites. "Endogenous gene" is used to differentiate from a "foreign gene", "transgene" or "chimeric gene", and refers to a gene from a plant of a certain plant genus, species or variety, which has not been introduced into that plant by transformation (i.e. it is not a "transgene"), but which is normally present in plants of that genus, species or variety, or which is introduced in that plant from plants of another plant genus, species or variety, in which it is normally present, by normal breeding techniques or by somatic hybridization, e.g., by protoplast fusion. Similarly, an "endogenous allele" of a gene is not introduced into a plant or plant tissue by plant transformation, but is, for example, generated by plant mutagenesis and/or selection or obtained by screening natural populations of plants, or by gene targeting. [42] "Expression of a gene" or "gene expression" refers to the process wherein a DNA region, which is operably linked to appropriate regulatory regions, particularly a promoter, is transcribed into an RNA molecule. The RNA molecule is then processed further (by post-transcriptional processes) within the cell, e.g. by RNA splicing and translation initiation and translation into an amino acid chain (protein), and translation termination by translation stop codons. The term "functionally expressed" is used herein to indicate that a functional protein is produced; the term "not functionally expressed" to indicate that a protein with significantly reduced or no functionality (biological activity) is produced or that no protein is produced (see further below).

[43] The term "protein" refers to a molecule consisting of a chain of amino acids, without reference to a specific mode of action, size, 3 -dimensional structure or origin. A "fragment" or "portion" of a PGAZ protein may thus still be referred to as a "protein". An "isolated protein" is used to refer to a protein that is no longer in its natural environment, for example in vitro or in a recombinant bacterial or plant host cell. "Amino acids" are the principal building blocks of proteins and enzymes. They are incorporated into proteins by transfer RNA according to the genetic code while messenger RNA is being decoded by ribosomes. During and after the final assembly of a protein, the amino acid content dictates the spatial and biochemical properties of the protein or enzyme. The amino acid backbone determines the primary sequence of a protein, but the nature of the side chains determines the protein's properties. "Similar amino acids", as used herein, refers to amino acids that have similar amino acid side chains, i.e. amino acids that have polar, non-polar or practically neutral side chains. "Non-similar amino acids", as used herein, refers to amino acids that have different amino acid side chains, for example an amino acid with a polar side chain is non-similar to an amino acid with a non-polar side chain. Polar side chains usually tend to be present on the surface of a protein where they can interact with the aqueous environment found in cells ("hydrophilic" amino acids). On the other hand, "non-polar" amino acids tend to reside within the center of the protein where they can interact with similar non-polar neighbors ("hydrophobic" amino acids"). Examples of amino acids that have polar side chains are arginine, asparagine, aspartate, cysteine, glutamine, glutamate, histidine, lysine, serine, and threonine (all hydrophilic, except for cysteine which is hydrophobic). Examples of amino acids that have non-polar side chains are alanine, glycine, isoleucine, leucine, methionine, phenylalanine, proline, and tryptophan (all hydrophobic, except for glycine which is neutral).

[44] The term "PGAZ gene" refers herein to a nucleic acid sequence encoding an abscission-related polygalacturonases (PGAZ) protein, which is an enzyme which depolymerizes pectin/ pectic acid by cleaving the glycosidic bonds by hydrolytic reaction. PGases belong to the glycoside hydrolase family 28.

[45] As used herein, the term "allele(s)" means any of one or more alternative forms of a gene at a particular locus. In a diploid (or amphidiploid) cell of an organism, alleles of a given gene are located at a specific location or locus (loci plural) on a chromosome. One allele is present on each chromosome of the pair of homologous chromosomes.

[46] As used herein, the term "homologous chromosomes" means chromosomes that contain information for the same biological features and contain the same genes at the same loci but possibly different alleles of those genes. Homologous chromosomes are chromosomes that pair during meiosis. "Non-homologous chromosomes", representing all the biological features of an organism, form a set, and the number of sets in a cell is called ploidy. Diploid organisms contain two sets of non-homologous chromosomes, wherein each homologous chromosome is inherited from a different parent. In amphidiploid species, essentially two sets of diploid genomes exist, whereby the chromosomes of the two genomes are referred to as "homeologous chromosomes" (and similarly, the loci or genes of the two genomes are referred to as homeologous loci or genes). A diploid, or amphidiploid, plant species may comprise a large number of different alleles at a particular locus. [47] As used herein, the term "heterozygous" means a genetic condition existing when two different alleles reside at a specific locus, but are positioned individually on corresponding pairs of homologous chromosomes in the cell. Conversely, as used herein, the term "homozygous" means a genetic condition existing when two identical alleles reside at a specific locus, but are positioned individually on corresponding pairs of homologous chromosomes in the cell.

[48] As used herein, the term "locus" (loci plural) means a specific place or places or a site on a chromosome where for example a gene or genetic marker is found. For example, the "PGAZ-A1 locus" refers to the position on a chromosome of the A genome where the PGAZ-A1 gene (and two PGAZ-A1 alleles) may be found; the "PGAZ-A2 locus" refers to the position on a chromosome of the A genome where the PGAZ-A2 gene (and two PGAZ-A2 alleles) may be found, while the" PGAZ-Cl locus" refers to the position on a chromosome of the C genome where the PGAZ-Cl gene (and two PGAZ-Cl alleles) may be found, and ths"PGAZ-C2 locus" refers to the position on a chromosome of the C genome where the PGAZ-C2 gene (and two PGAZ-C2 alleles) may be found.

[49] Whenever reference to a "plant" or "plants" according to the invention is made, it is understood that also plant parts (cells, tissues or organs, seed pods, seeds, severed parts such as roots, leaves, flowers, pollen, etc.), progeny of the plants which retain the distinguishing characteristics of the parents (especially the fruit dehiscence properties), such as seed obtained by selling or crossing, e.g. hybrid seed (obtained by crossing two inbred parental lines), hybrid plants and plant parts derived there from are encompassed herein, unless otherwise indicated. [50] A "molecular assay" (or test) refers herein to an assay that indicates (directly or indirectly) the presence or absence of one or more particular PGAZ alleles at one or more PGAZ loci (e.g., for Brassica napus, at one or more of the PGAZ -Al, PGAZ-A2, PGAZ -CI, PGAZ-C2 loci). In one embodiment it allows one to determine whether a particular (wild type or mutant) PGAZ allele is homozygous or heterozygous at the locus in any individual plant. [51] "Wild type" (also written "wildtype" or "wild-type"), as used herein, refers to a typical form of a plant or a gene as it most commonly occurs in nature. A "wild type plant" refers to a plant with the most common phenotype of such plant in the natural population. A "wild type allele" refers to an allele of a gene required to produce the wild-type phenotype. By contrast, a "mutant plant" refers to a plant with a different rare phenotype of such plant in the natural population or produced by human intervention, e.g. by mutagenesis, and a "mutant allele" refers to an allele of a gene required to produce the mutant phenotype.

[52] As used herein, the term "wild type PGAZ", means a naturally occurring PGAZ allele found within plants, in particular Brassicacea plants, especially Brassica plants, which encodes a functional PGAZ protein. [53] In contrast, the term "mutant PGAZ as used herein, refers to a PGAZ allele, which does not encode a functional PGAZ protein, i.e. a PGAZ allele encoding a non- functional PGAZ protein, which, as used herein, refers to a PGAZ protein having no biological activity or a significantly reduced biological activity as compared to the corresponding wild-type functional PGAZ protein, or encoding no PGAZ protein at all. Such a "mutant PGAZ allele" (also called "full knock-out" or "null" allele) is a wild-type PGAZ allele, which comprises one or more mutations in its nucleic acid sequence, whereby the mutation(s) preferably result in a significantly reduced (absolute or relative) amount of functional PGAZ protein in the cell in vivo. As used herein, a "full knock-out PGAZ allele" is a mutant PGAZ allele the presence of which results in an increase of pod drop resistance in that plant. Mutant alleles of the PGAZ protein-encoding nucleic acid sequences are designated as "pgaz" (e.g., for Brassica napus, pgaz-al, pgaz-a2, pgaz-cl or pgaz-c2, respectively) herein. Mutant alleles can be either "natural mutant" alleles, which are mutant alleles found in nature (e.g. produced spontaneously without human application of mutagens) or "induced mutant" alleles, which are induced by human intervention, e.g. by mutagenesis. [54] A "full knock-out mutant PGAZ allele" is, for example, a wild-type PGAZ allele, which comprises one or more mutations in its nucleic acid sequence, for example, one or more non-sense or mis-sense mutations. In particular, such a full knock-out mutant PGAZ allele is a wild-type PGAZ allele, which comprises a mutation that preferably result in the production of a PGAZ protein lacking at least one conserved motif, such as the NTD motif (substrate-binding region), comprising residues NTDG at positions corresponding to positions 241-244 of SEQ ID NO: 3; the DD motif (catalytic region), comprising residues GDDC at positions corresponding to positions 263-266 of SEQ ID NO: 3; the GHG motif (catalytic region) comprising residues GHGISIGSLG at positions corresponding to positions 286- 295 of SEQ ID NO: 3, and the RIK motif (substrate-binding region) comprising residues RIK at positions corresponding to positions 322-324 of SEQ ID NO: 3, or lacking at least one amino acid critical for its function, such as the catalytic amino acid D at a position corresponding to position 264 of SEQ ID NO: 3, and H at a position corresponding to position 287 of SEQ ID NO: 3, such that the biological activity of the PGAZ protein is reduced or completely abolished, or whereby the mutation(s) preferably result in a significantly reduced amount of functional PGAZ protein, or no production of a PGAZ protein. [55] A "corresponding position" or "a position corresponding to position" in accordance with the present invention it is to be understood that nucleotides/amino acids may differ in the indicated number but may still have similar neighbouring nucleotides/amino acids. Said nucleotides/amino acids which may be exchanged, deleted or added are also comprised by the term "corresponding position".

[56] In order to determine whether a nucleotide residue or amino acid residue in a given PGAZ nucleotide/amino acid sequence corresponds to a certain position in the nucleotide sequence of another PGAZ nucleotide or amino acid sequence, the skilled person can use means and methods well-known in the art, e.g., alignments, either manually or by using computer programs such as BLAST (Altschul et al. (1990), Journal of Molecular Biology, 215, 403-410), which stands for Basic Local Alignment Search Tool or ClustalW (Thompson et al. (1994), Nucleic Acid Res., 22, 4673-4680) or any other suitable program which is suitable to generate sequence alignments. For an alignment of the Arabidopsis and Brassica PGAZ amino acid sequences, see for example, Figure 5.

[57] A "significantly reduced amount of functional PGAZ protein" refers to a reduction in the amount of a functional PGAZ protein produced by the cell comprising a mutant PGAZ allele by at least 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95% or 100% (i.e. no functional PGAZ protein is produced by the cell) as compared to the amount of the functional PGAZ protein produced by the cell not comprising the mutant PGAZ allele. This definition encompasses the production of a "non- functional" PGAZ protein (e.g. truncated PGAZ protein) having no biological activity in vivo, the reduction in the absolute amount of the functional PGAZ protein (e.g. no functional PGAZ protein being made due to the mutation in the PGAZ gene), the production of a PGAZ protein with significantly reduced biological activity compared to the activity of a functional wild type PGAZ protein (such as a PGAZ protein in which one or more amino acid residues that are crucial for the biological activity of the encoded PGAZ protein, as exemplified below, are substituted for another amino acid residue) and/or the adverse effect of dominant negative PGAZ proteins on other functional and/or partially functional PGAZ proteins.

[58] The term "mutant PGAZ protein", as used herein, refers to a PGAZ protein encoded by a mutant PGAZ nucleic acid sequence ("pgaz allele") whereby the mutation results in a significantly reduced and/or no PGAZ activity in vivo, compared to the activity of the PGAZ protein encoded by a non- mutant, wild type PGAZ sequence ("PGAZ allele").

[59] "Mutagenesis", as used herein, refers to the process in which plant cells (e.g., a plurality of Brassica seeds or other parts, such as pollen, etc.) are subjected to a technique which induces mutations in the DNA of the cells, such as contact with a mutagenic agent, such as a chemical substance (such as ethylmethylsulfonate (EMS), ethylnitrosourea (ENU), etc.) or ionizing radiation (neutrons (such as in fast neutron mutagenesis, etc.), alpha rays, gamma rays (such as that supplied by a Cobalt 60 source), X- rays, UV-radiation, etc.), or a combination of two or more of these. Thus, the desired mutagenesis of one or more PGAZ alleles may be accomplished by use of chemical means such as by contact of one or more plant tissues with ethylmethylsulfonate (EMS), ethylnitrosourea, etc., by the use of physical means such as x-ray, etc, or by gamma radiation, such as that supplied by a Cobalt 60 source. While mutations created by irradiation are often large deletions or other gross lesions such as translocations or complex rearrangements, mutations created by chemical mutagens are often more discrete lesions such as point mutations. For example, EMS alkylates guanine bases, which results in base mispairing: an alkylated guanine will pair with a thymine base, resulting primarily in G/C to A/T transitions. Following mutagenesis, Brassica plants are regenerated from the treated cells using known techniques. For instance, the resulting Brassica seeds may be planted in accordance with conventional growing procedures and following self-pollination seed is formed on the plants. Alternatively, doubled haploid plantlets may be extracted to immediately form homozygous plants, for example as described by Coventry et al. (1988, Manual for Microspore Culture Technique for Brassica napus. Dep. Crop Sci. Techn. Bull. OAC Publication 0489. Univ. of Guelph, Guelph, Ontario, Canada). Additional seed that is formed as a result of such self-pollination in the present or a subsequent generation may be harvested and screened for the presence of mutant PGAZ alleles. Several techniques are known to screen for specific mutant alleles, e.g., Deleteagene™ (Delete-a-gene; Li et al., 2001, Plant J 27: 235-242) uses polymerase chain reaction (PCR) assays to screen for deletion mutants generated by fast neutron mutagenesis, TILLING (targeted induced local lesions in genomes; McCallum et al., 2000, Nat Biotechnol 18:455-457) identifies EMS-induced point mutations, etc. Additional techniques to screen for the presence of specific mutant PGAZ alleles are described in the Examples below. Mutagenesis can comprise random mutagenesis, or can comprise targeted mutagenesis. Mutagenesis can also result in epimutations that cause epigenetic silencing.

[60] The term "gene targeting" refers herein to directed gene modification that uses mechanisms such as homologous recombination, mismatch repair or site-directed mutagenesis. The method can be used to replace, insert and delete endogenous sequences or sequences previously introduced in plant cells. Methods for gene targeting can be found in, for example, WO 2006/105946 or WO2009/002150.

[61] As used herein, the term "non-naturally occurring" or "cultivated" when used in reference to a plant, means a plant with a genome that has been modified by man. A transgenic plant, for example, is a non-naturally occurring plant that contains an exogenous nucleic acid molecule, e.g., a chimeric gene comprising a transcribed region which when transcribed yields a biologically active RNA molecule capable of reducing the expression of an endogenous gene, such as a PGAZ gene, and, therefore, has been genetically modified by man. In addition, a plant that contains a mutation in an endogenous gene, for example, a mutation in an endogenous PGAZ gene, (e.g. in a regulatory element or in the coding sequence) as a result of an exposure to a mutagenic agent is also considered a non-naturally plant, since it has been genetically modified by man. Furthermore, a plant of a particular species, such as Brassica napus, that contains a mutation in an endogenous gene, for example, in an endogenous PGAZ gene, that in nature does not occur in that particular plant species, as a result of, for example, directed breeding processes, such as marker-assisted breeding and selection or introgression, with a plant of the same or another species, such as Brassica juncea or rapa, of that plant is also considered a non-naturally occurring plant. In contrast, a plant containing only spontaneous or naturally occurring mutations, i.e. a plant that has not been genetically modified by man, is not a "non-naturally occurring plant" as defined herein and, therefore, is not encompassed within the invention. One skilled in the art understands that, while a non-naturally occurring plant typically has a nucleotide sequence that is altered as compared to a naturally occurring plant, a non-naturally occurring plant also can be genetically modified by man without altering its nucleotide sequence, for example, by modifying its methylation pattern. ₅

[62] The term "ortholog" of a gene or protein refers herein to the homologous gene or protein found in another species, which has the same function as the gene or protein, but is (usually) diverged in sequence from the time point on when the species harboring the genes diverged (i.e. the genes evolved from a common ancestor by speciation). Orthologs of the Brassica napus PGAZ genes may thus be identified in other plant species (e.g. other pod-bearing plant species, such as other Brassicaceae plants, or Fabaceae plants such as, for example, Phaseolus species, or soybeans {Glycine max)) based on both sequence comparisons (e.g. based on percentages sequence identity over the entire sequence or over specific domains) and/or functional analysis.

[63] A "variety" is used herein in conformity with the UPOV convention and refers to a plant grouping within a single botanical taxon of the lowest known rank, which grouping can be defined by the expression of the characteristics resulting from a given genotype or combination of genotypes, can be distinguished from any other plant grouping by the expression of at least one of the said

characteristics and is considered as a unit with regard to its suitability for being propagated unchanged (stable). [64] The term "comprising" is to be interpreted as specifying the presence of the stated parts, steps or components, but does not exclude the presence of one or more additional parts, steps or components. A plant comprising a certain trait may thus comprise additional traits.

[65] It is understood that when referring to a word in the singular (e.g. plant or root), the plural is also included herein (e.g. a plurality of plants, a plurality of roots). Thus, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

[66] For the purpose of this invention, the "sequence identity" of two related nucleotide or amino acid sequences, expressed as a percentage, refers to the number of positions in the two optimally aligned sequences which have identical residues (xlOO) divided by the number of positions compared. A gap, i.e., a position in an alignment where a residue is present in one sequence but not in the other, is regarded as a position with non-identical residues. The "optimal alignment" of two sequences is found by aligning the two sequences over the entire length according to the Needleman and Wunsch global alignment algorithm (Needleman and Wunsch, 1970, J Mol Biol 48(3):443-53) in The European Molecular Biology Open Software Suite (EMBOSS, Rice et al, 2000, Trends in Genetics 16(6): 276— 277; see e.g. http://www.ebi.ac.uk/emboss/align/index.html) using default settings (gap opening penalty = 10 (for nucleotides) / 10 (for proteins) and gap extension penalty = 0.5 (for nucleotides) / 0.5 (for proteins)). For nucleotides the default scoring matrix used is EDNAFULL and for proteins the default scoring matrix is EBLOSUM62. [67] "Substantially identical" or "essentially similar", as used herein, refers to sequences, which, when optimally aligned as defined above, share at least a certain minimal percentage of sequence identity (as defined further below).

[68] "Stringent hybridization conditions" can be used to identify nucleotide sequences, which are substantially identical to a given nucleotide sequence. Stringent conditions are sequence dependent and will be different in different circumstances. Generally, stringent conditions are selected to be about 5°C lower than the thermal melting point (T_m) for the specific sequences at a defined ionic strength and pH. The T_m is the temperature (under defined ionic strength and pH) at which 50% of the target sequence hybridizes to a perfectly matched probe. Typically stringent conditions will be chosen in which the salt concentration is about 0.02 molar at pH 7 and the temperature is at least 60°C. Lowering the salt concentration and/or increasing the temperature increases stringency. Stringent conditions for RNA- DNA hybridizations (Northern blots using a probe of e.g. lOOnt) are for example those which include at least one wash in 0.2X SSC at 63°C for 20min, or equivalent conditions.

[69] "High stringency conditions" can be provided, for example, by hybridization at 65°C in an aqueous solution containing 6x SSC (20x SSC contains 3.0 M NaCl, 0.3 M Na-citrate, pH 7.0), 5x Denhardt's (100X Denhardt's contains 2%> Ficoll, 2%> Polyvinyl pyrollidone, 2%> Bovine Serum

Albumin), 0.5%> sodium dodecyl sulphate (SDS), and 20 μg/ml denaturated carrier DNA (single- stranded fish sperm DNA, with an average length of 120 - 3000 nucleotides) as non-specific competitor. Following hybridization, high stringency washing may be done in several steps, with a final wash (about 30 min) at the hybridization temperature in 0.2-0.1 SSC, 0.1% SDS.

[70] "Moderate stringency conditions" refers to conditions equivalent to hybridization in the above described solution but at about 60-62°C. Moderate stringency washing may be done at the hybridization temperature in lx SSC, 0.1% SDS.

[71] "Low stringency" refers to conditions equivalent to hybridization in the above described solution at about 50-52°C. Low stringency washing may be done at the hybridization temperature in 2x SSC, 0.1% SDS. See also Sambrook et al. (1989) and Sambrook and Russell (2001).

[72] "Increased yield" or "increased harvested yield" or "increased seed or grain yield" refers to the larger amount of seed or grain harvested from a plurality of plants, each comprising mutant PGAZ alleles according to the invention, when compared to the amount of seed or grain harvested from a similar number of isogenic plants without the mutant PGAZ alleles. Yield is typically expressed in volume units of harvested seed per surface units, such as bushels/acre or kg/ha. The yield increase is typically expressed in percentage, whereby the yield of the reference or control plant is referred to as 100%) and the yield of the plants according to the inventions is expressed in %> relative to the yield of the control plant. Yield increase may be a yield of at least 101%), of at least 102%, of at least 103%), of at least 105%, of at least 108%, of at least 110%.

DETAILED DESCRIPTION

[73] Brassica napus (genome AACC, 2n=4x=38), which is an allotetraploid (amphidiploid) species containing essentially two diploid genomes (the A and the C genome) due to its origin from diploid ancestors. Brassica napus comprises four PGAZ genes in its genome; two PGAZ genes are located on the A genome (hereinafter called PGAZ-A1 and PGAZ-A2) and two PGAZ genes are located on the C genome, herein after called PGAZ-Cl and PGAZ-C2. It was found by the inventors that the presence of mutant alleles of the PGAZ alleles increase pod drop resistance, and that the more mutant PGAZ alleles are present, the higher the pod drop resistance. [74] The application relates to Brassica plants in which expression of PGAZ is functionally reduced. Functionally reduced expression can be reduction in PGAZ protein production and/or activity.

[75] Thus, in a first aspect, a Brassica plant is provided comprising at least two PGAZ genes, characterised in that it comprises at least one mutant PGAZ allele in its genome. In a further aspect, said mutant PGAZ allele is a mutant allele of a PGAZ gene comprising a nucleic acid sequence selected from the group consisting of:

a nucleotide sequence which comprises at least 90%> sequence identity to SEQ ID NO: 1, SEQ ID NO: 4, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 13, SEQ ID NO: 16, SEQ ID NO: 19, SEQ ID NO: 22, SEQ ID NO: 25, SEQ ID NO: 28, SEQ ID NO: 31, SEQ ID NO: 34, SEQ ID NO: 37, SEQ ID NO: 40, or SEQ ID NO: 43;

- a nucleotide sequence comprising a coding sequence which comprises at least 90%> sequence identity to SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 8, SEQ ID NO: 11, SEQ ID NO: 14, SEQ ID NO: 17, SEQ ID NO: 20, SEQ ID NO: 23, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 32, SEQ ID NO: 35, SEQ ID NO: 38, SEQ ID NO: 41, or SEQ ID NO: 44; and a nucleotide sequence encoding an amino acid sequence which comprises at least 90%> sequence identity to SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 12, SEQ

[76] In a further aspect, the plant according to the invention is a Brassica plant comprising four PGAZ genes, said Brassica plant selected from the group consisting of Brassica napus, Brassica juncea and Brassica carinata. In another embodiment, the plant according to the invention comprises comprising at least two mutant PGAZ alleles, or at least three mutant PGAZ alleles, or at least four mutant PGAZ alleles, or at least five mutant PGAZ alleles, or at least six mutant PGAZ alleles, or at least seven mutant PGAZ alleles, or at least eight mutant PGAZ alleles. [77] In yet another embodiment, the plants according to the invention comprise a mutant PGAZ allele selected from the group consisting of:

position 2140 of SEQ ID NO: 4;

position 3275 of SEQ ID NO: 7;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2473 of SEQ ID NO: 13. [78] In again a further embodiment, said plant is homozygous for the mutant PGAZ allele. In yet another embodiment, said plant has increased pod drop resistance. A further embodiment provides a plant cell, pod, seed or progeny of the plant according to the invention.

[79] In yet another embodiment, a Brassica plant is provided comprising at least two PGAZ genes, wherein expression of at least one PGAZ gene is reduced. Expression can be reduced, for example, by introduction of a chimeric gene into said plant comprising a DNA region yielding an RNA molecule inhibitory to one or more PGAZ genes. In one embodiment, said plant comprises a chimeric gene, said chimeric gene comprising the following operably linked DNA fragments:

i. a plant-expressible promoter;

ii. a DNA region, which when transcribed yields an RNA or protein molecule inhibitory to one or more PGAZ genes encoding; and, optionally,

iii. a 3 ' end region involved in transcription termination and polyadenylation. - -

[80] Said DNA region may yield a sense RNA molecule capable of down-regulating expression of one or more PGAZ genes by co-suppression. The transcribed DNA region will yield upon transcription a so-called sense RNA molecule capable of reducing the expression of a PGAZ gene in the target plant or plant cell in a transcriptional or post-transcriptional manner. The transcribed DNA region (and resulting RNA molecule) comprises at least 20 consecutive nucleotides having at least 95% sequence identity to the nucleotide sequence of one or more PGAZ genes present in the plant cell or plant.

[81] Said DNA region may also yield an antisense RNA molecule capable of down-regulating expression of one or more PGAZ genes. The transcribed DNA region will yield upon transcription a so- called antisense RNA molecule capable of reducing the expression of a PGAZ gene in the target plant or plant cell in a transcriptional or post-transcriptional manner. The transcribed DNA region (and resulting RNA molecule) comprises at least 20 consecutive nucleotides having at least 95% sequence identity to the complement of the nucleotide sequence of one or more functional PGAZ genes present in the plant cell or plant. [82] The minimum nucleotide sequence of the antisense or sense RNA region of about 20 nt of the PGAZ gene may be comprised within a larger RNA molecule, varying in size from 20 nt to a length equal to the size of the target gene. The mentioned antisense or sense nucleotide regions may thus be about from about 21 nt to about 1300 nt long, such as 21 nt, 40 nt, 50 nt, 100 nt, 200 nt, 300 nt, 500 nt, 1000 nt, or even about 1300 nt or larger in length. Moreover, it is not required for the purpose of the invention that the nucleotide sequence of the used inhibitory PGAZ RNA molecule or the encoding region of the transgene, is completely identical or complementary to the endogenous PGAZ gene the expression of which is targeted to be reduced in the plant cell. The longer the sequence, the less stringent the requirement for the overall sequence identity is. Thus, the sense or antisense regions may have an overall sequence identity of about 40 % or 50 % or 60 % or 70 % or 80 % or 90 % or 100 % to the nucleotide sequence of the endogenous PGAZ gene or the complement thereof. However, as mentioned, antisense or sense regions should comprise a nucleotide sequence of 20 consecutive nucleotides having about 95 to about 100 % sequence identity to the nucleotide sequence of the endogenous PGAZ gene. The stretch of about 95 to about 100% sequence identity may be about 50, 75 or 100 nt. It will be clear that all combinations between mentioned length and sequence identity can be made, both in sense and/or antisense orientation.

[83] The efficiency of the above mentioned chimeric genes for antisense RNA or sense RNA- mediated gene expression level down-regulation may be further enhanced by inclusion of DNA elements which result in the expression of aberrant, non-polyadenylated PGAZ inhibitory RNA molecules. One such DNA element suitable for that purpose is a DNA region encoding a self-splicing ribozyme, as described in WO 00/01133. The efficiency may also be enhanced by providing the generated RNA molecules with nuclear localization or retention signals as described in WO 03/076619. [84] Said DNA region may also yield a double-stranded RNA molecule capable of down-regulating PGAZ gene expression. Upon transcription of the DNA region the RNA is able to form dsRNA molecule through conventional base paring between a sense and antisense region, whereby the sense and antisense region are nucleotide sequences as hereinbefore described. dsRNA-encoding PGAZ expression-reducing chimeric genes according to the invention may further comprise an intron, such as a heterologous intron, located e.g. in the spacer sequence between the sense and antisense RNA regions in accordance with the disclosure of WO 99/53050 (incorporated herein by reference). To achieve the construction of such a transgene, use can be made of the vectors described in WO 02/059294 Al .

[85] Said DNA region may also yield a pre-miRNA molecule which is processed into a miRNA capable of guiding the cleavage of PGAZ mRNA. miRNAs are small endogenous RNAs that regulate gene expression in plants, but also in other eukaryotes. In plants, these about 21 nucleotide long RNAs are processed from the stem-loop regions of long endogenous pre-miRNAs by the cleavage activity of DICERLIKEl (DCL1). Plant miRNAs are highly complementary to conserved target mRNAs, and guide the cleavage of their targets. miRNAs appear to be key components in regulating the gene expression of complex networks of pathways involved inter alia in development.

[86] As used herein, a "miRNA" is an RNA molecule of about 20 to 22 nucleotides in length which can be loaded into a RISC complex and direct the cleavage of a target RNA molecule, wherein the target RNA molecule comprises a nucleotide sequence essentially complementary to the nucleotide sequence of the miRNA molecule whereby one or more of the following mismatches may occur:

- A mismatch between the nucleotide at the 5' end of said miRNA and the corresponding nucleotide sequence in the target RNA molecule;

- A mismatch between any one of the nucleotides in position 1 to position 9 of said miRNA and the corresponding nucleotide sequence in the target RNA molecule;

- Three mismatches between any one of the nucleotides in position 12 to position 21 of said miRNA and the corresponding nucleotide sequence in the target RNA molecule provided that there are no more than two consecutive mismatches.

No mismatch is allowed at positions 10 and 11 of the miRNA (all miRNA positions are indicated starting from the 5' end of the miRNA molecule).

[87] As used herein, a "pre-miRNA" molecule is an RNA molecule of about 100 to about 200 nucleotides, preferably about 100 to about 130 nucleotides which can adopt a secondary structure comprising a dsRNA stem and a single stranded RNA loop and further comprising the nucleotide sequence of the miRNA and its complement sequence of the miRNA* in the double-stranded RNA stem. Preferably, the miRNA and its complement are located about 10 to about 20 nucleotides from the free ends of the miRNA dsRNA stem. The length and sequence of the single stranded loop region are not critical and may vary considerably, e.g. between 30 and 50 nt in length. Preferably, the difference in free energy between unpaired and paired RNA structure is between -20 and -60 kcal/mole, particularly around -40 kcal/mole. The complementarity between the miRNA and the miRNA* do not need to be perfect and about 1 to 3 bulges of unpaired nucleotides can be tolerated. The secondary structure adopted by an RNA molecule can be predicted by computer algorithms conventional in the art such as mFold, UNAFold and RNAFold. The particular strand of the dsRNA stem from the pre-miRNA which is released by DCL activity and loaded onto the RISC complex is determined by the degree of complementarity at the 5' end, whereby the strand which at its 5' end is the least involved in hydrogen bounding between the nucleotides of the different strands of the cleaved dsRNA stem is loaded onto the RISC complex and will determine the sequence specificity of the target RNA molecule degradation. However, if empirically the miRNA molecule from a particular synthetic pre-miRNA molecule is not functional because the "wrong" strand is loaded on the RISC complex, it will be immediately evident that this problem can be solved by exchanging the position of the miRNA molecule and its complement on the respective strands of the dsRNA stem of the pre-miRNA molecule. As is known in the art, binding between A and U involving two hydrogen bounds, or G and U involving two hydrogen bounds is less strong that between G and C involving three hydrogen bounds. [88] miRNA molecules may be comprised within their naturally occurring pre-miRNA molecules but they can also be introduced into existing pre-miRNA molecule scaffolds by exchanging the nucleotide sequence of the miRNA molecule normally processed from such existing pre-miRNA molecule for the nucleotide sequence of another miRNA of interest. The scaffold of the pre-miRNA can also be completely synthetic. Likewise, synthetic miRNA molecules may be comprised within, and processed from, existing pre-miRNA molecule scaffolds or synthetic pre-miRNA scaffolds.

[89] Also suitable to the invention is a Brassica plant comprising at least two PGAZ genes, wherein PGAZ protein activity is reduced, such as a Brassica plant comprising a DNA construct plant which encodes a dominant-negative PGAZ protein, or a DNA construct which encodes inactivating antibodies to PGAZ proteins, or a DNA construct encoding a protein which specifically inactivates the PGAZ protein, such as a protein with a specific PGAZ binding domain and a protein cleavage activity.

"Inactivating antibodies to PGAZ proteins" are antibodies or parts thereof which specifically bind at least to some epitopes of PGAZ proteins, and which inhibit the activity of the target protein. PGAZ protein activity can also be reduced, for example, by aggregating PGAZ proteins (see, e.g.,

WO2007/071789), or by scaffolding target proteins (see, e.g., WO2009/030780). [90] Said Brassica plant comprising at least two PGAZ genes, wherein expression of at least one PGAZ gene is reduced, can, for example, be a Brassica plant comprising four PGAZ genes, said Brassica plant selected from the group consisting of Brassica napus, Brassica juncea and Brassica carinata. In said Brassica plant, expression of at least one, or at least two, or at least three, or four PGAZ genes can be reduced. - -

[91] The plants according to the invention may, according to this invention, be used for breeding purposes.

[92] In another aspect of the invention, a mutant allele of a Brassica PGAZ gene is provided, wherein the PGAZ gene is selected from the group consisting of:

a nucleotide sequence comprising a coding sequence which comprises at least 90% sequence identity to SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 8, SEQ ID NO: 11, SEQ ID NO: 14,

SEQ ID NO: 17, SEQ ID NO: 20, SEQ ID NO: 23, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 32, SEQ ID NO: 35, SEQ ID NO: 38, SEQ ID NO: 41, or SEQ ID NO: 44; and a nucleotide sequence encoding an amino acid sequence which comprises at least 90%> sequence identity to SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 12, SEQ ID NO: 15, SEQ ID NO: 18, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 27, SEQ ID

NO: 30, SEQ ID NO: 33, SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, or SEQ ID NO: 45.

[93] In another embodiment, said mutant allele is selected from the group consisting of:

position 3356 of SEQ ID NO: 7;

position 2442 of SEQ ID NO: 10; a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2464 of SEQ ID NO: 13;

a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2473 of SEQ ID NO: 13. [94] Also provided are methods of generating and combining mutant and wild type PGAZ alleles in Brassica plants, whereby pod drop is reduced in these plants. The use of these plants for transferring mutant PGAZ alleles to other plants is also an embodiment of the invention, as are the plant products of any of the plants described. In addition kits and methods for marker assisted selection (MAS) for combining or detecting PGAZ genes and/or alleles are provided. Each of the embodiments of the invention is described in detail herein below.

[95] The plants described herein which exhibit increased pod drop resistance may have an increase in the yield of harvested seed.

Nucleic acids according to the invention

[96] Provided are both wild type PGAZ nucleic acid sequences encoding functional PGAZ proteins and mutant pgaz nucleic acid sequences (comprising one or more mutations, preferably mutations which result in no or a significantly reduced biological activity of the encoded PGAZ protein or in no PGAZ protein being produced) of PGAZ genes from Brassicaceae, particularly from Brassica species, especially from Brassica napus, but also from other Brassica crop species. For example, Brassica species comprising an A and/or a C genome may comprise different alleles of PGAZ- A or PGAZ-C genes, which can be identified and combined in a single plant according to the invention. In addition, mutagenesis or gene targeting methods can be used to generate mutations in wild type PGAZ alleles, thereby generating mutant pgaz alleles for use according to the invention. Because specific PGAZ alleles are preferably combined in a plant by crossing and selection, in one embodiment the PGAZ and/or pgaz nucleic acid sequences are provided within a plant (i.e. endogenously), e.g. a Brassica plant, preferably a Brassica plant which can be crossed with Brassica napus or which can be used to make a "synthetic" Brassica napus plant. Hybridization between different Brassica species is described in the art, e.g., as referred to in Snowdon (2007, Chromosome research 15: 85-95). Interspecific hybridization can, for example, be used to transfer genes from, e.g., the C genome in B. napus (AACC) to the C genome in B. carinata (BBCC), or even from, e.g., the C genome in B. napus (AACC) to the B genome in B. juncea (AABB) (by the sporadic event of illegitimate recombination between their C and B genomes).

"Resynthesized" or "synthetic" Brassica napus lines can be produced by crossing the original ancestors, B. oleracea (CC) and B. rapa (AA). Interspecific, and also intergeneric, incompatibility barriers can be successfully overcome in crosses between Brassica crop species and their relatives, e.g., by embryo rescue techniques or protoplast fusion (see e.g. Snowdon, above). [97] However, isolated PGAZ and pgaz nucleic acid sequences (e.g. isolated from the plant by cloning or made synthetically by DNA synthesis), as well as variants thereof and fragments of any of these are also provided herein, as these can be used to determine which sequence is present

endogenously in a plant or plant part, whether the sequence encodes a functional, a non- functional or no protein (e.g. by expression in a recombinant host cell as described below) and for selection and transfer of specific alleles from one plant into another, in order to generate a plant having the desired combination of functional and mutant alleles.

[98] Nucleic acid sequences of PGAZ genes have been isolated from two Brassica napus lines (BnPGAZ-Al, BnPGAZ-A2, BnPGAZ-Cl, and BnPGAZ-C2), from Brassica rapa (BrPGAZ-Al and BrPGAZ-A2), Brassica oleracea (BoPGAZ-Cl and BoPGAZ-C2), and Brasisca nigra (BniPGAZ-Bl and BniPGAZ-B2) as depicted in the sequence listing. The wild type PGAZ sequences are depicted, while the mutant pgaz sequences of these sequences, and of sequences essentially similar to these, are described herein below and in the Examples, with reference to the wild type PGAZ sequences. The genomic PGAZ protein-encoding DNA from Brassica napus, Brassica rapa, Brassica oleracea and Brassica nigra contains seven introns.

[99] "PGAZ-A1 nucleic acid sequences" or "PGAZ-A1 variant nucleic acid sequences" according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 6, 18, and 30, or nucleic acid sequences having at least 80%>, at least 85%>, at least 90%>, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 4, 16 and 28, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%o, 99%) or 100%) sequence identity with any one of SEQ ID NOs: 5, 17 and 19. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing. [100] "PGAZ-A2 nucleic acid sequences" or "PGAZ-A2 variant nucleic acid sequences" according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%>, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 9, 21, and 33, or nucleic acid sequences having at least 80%), at least 85%>, at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 7, 19 and 31, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 8, 20 and 32. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[101] "PGAZ-C1 nucleic acid sequences" or "PGAZ-C1 variant nucleic acid sequences" according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%>, at least ₅

80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 12, 24, and 36, or nucleic acid sequences having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 10, 22 and 34, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 11, 23 and 35. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[102] "PGAZ-C2 nucleic acid sequences" or "PGAZ-C2 variant nucleic acid sequences" according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with any one of

SEQ ID NOs: 15, 27, and 39, or nucleic acid sequences having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 13, 25 and 37, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs: 14, 26 and 38. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[103] "PGAZ-B1 nucleic acid sequences" or "PGAZ-B1 variant nucleic acid sequences", or

"BniPGAZ-B 1 nucleic acid sequences" or "PGAZ-B 1 nucleic acid sequences from Brassica nigra" or "Brassica nigra PGAZ-B 1 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 42, or nucleic acid sequences having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 40, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 41. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[104] "PGAZ-B2 nucleic acid sequences" or "PGAZ-B2 variant nucleic acid sequences", or

"BniPGAZ-B2 nucleic acid sequences" or "PGAZ-B2 nucleic acid sequences from Brassica nigra" or "Brassica nigra PGAZ-B2 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 45, or nucleic acid sequences having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 43, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 44. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing. [105] "BnPGAZ-Al nucleic acid sequences" or "PGAZ-A1 nucleic acid sequences from Brassica napus" or "Brassica napus PGAZ-A1 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 6 or SEQ ID NO: 18, or nucleic acid sequences having at least 80%, at least 85%, at least 90%>, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 4 or SEQ ID NO: 16, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99%) or 100%) sequence identity with SEQ ID NO: 5 or SEQ ID NO: 17. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[106] "BnPGAZ-A2 nucleic acid sequences" or "PGAZ-A2 nucleic acid sequences from Brassica napus" or "Brassica napus PGAZ-A2 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 9 or SEQ ID NO: 21, or nucleic acid sequences having at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 7 or SEQ ID NO: 19, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 8 or SEQ ID NO: 20. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[107] "BnPGAZ-Cl nucleic acid sequences" or "PGAZ-C1 nucleic acid sequences from Brassica napus" or "Brassica napus PGAZ-C1 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%), at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 12 or SEQ ID NO: 24, or nucleic acid sequences having at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 10 or SEQ ID NO: 22, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 11 or SEQ ID NO: 23. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[108] "BnPGAZ-C2 nucleic acid sequences" or "PGAZ-C2 nucleic acid sequences from Brassica napus" or "Brassica napus PGAZ-C2 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%), at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 15 or SEQ ID NO: 27, or nucleic acid sequences having at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 13 or SEQ ID NO: 25, or _? having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 14 or SEQ ID NO: 26. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing. [109] "BrPGAZ-Al nucleic acid sequences" or "PGAZ-A1 nucleic acid sequences from Brassica rapa" or "Brassica rapa PGAZ-A1 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 30, or nucleic acid sequences having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%), 99%) or 100%) sequence identity with SEQ ID NO: 28, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 29. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[110] "BrPGAZ-A2 nucleic acid sequences" or "PGAZ-A2 nucleic acid sequences from Brassica rapa" or "Brassica rapa PGAZ-A2 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 33, or nucleic acid sequences having at least 80%), at least 85%), at least 90%), at least 95%, 96%), 97%), 98%), 99%) or 100%) sequence identity with SEQ ID NO: 31, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with

SEQ ID NO: 32. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[I l l] "BoPGAZ-Cl nucleic acid sequences" or "PGAZ-Cl nucleic acid sequences from Brassica oleracea" or "Brassica oleracea PGAZ-Cl nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%), at least

80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 36, or nucleic acid sequences having at least 80%), at least 85%), at least 90%), at least 95%), 96%), 97%), 98%), 99%) or 100%) sequence identity with SEQ ID NO: 34, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 35. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[112] "BoPGAZ-C2 nucleic acid sequences" or "PGAZ-C2 nucleic acid sequences from Brassica oleracea" or "Brassica oleracea PGAZ-C2 nucleic acid sequences" or variants thereof, according to the invention are nucleic acid sequences encoding an amino acid sequence having at least 75%), at least 80%, at least 85%, at least 90%, at least 95%, 98%, 99% or 100% sequence identity with SEQ ID NO: 39, or nucleic acid sequences having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%), 99%) or 100%) sequence identity with SEQ ID NO: 37, or having a cDNA sequence having at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 38. These nucleic acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[113] Thus the invention provides both nucleic acid sequences encoding wild type, functional PGAZ proteins, including variants and fragments thereof (as defined further below), as well as mutant nucleic acid sequences of any of these, whereby the mutation in the nucleic acid sequence preferably results in one or more amino acids being inserted, deleted or substituted in comparison to the wild type PGAZ protein. Preferably the mutation(s) in the nucleic acid sequence result in one or more amino acid changes (i.e. in relation to the wild type amino acid sequence one or more amino acids are inserted, deleted and/or substituted) whereby the biological activity of the PGAZ protein is significantly reduced or completely abolished. A significant reduction in or complete abolishment of the biological activity of the PGAZ protein refers herein to a reduction in or abolishment of the substrate binding activity and/or the catalytic capacity of the PGAZ protein, such that the pod drop resistance of a plant expressing the mutant PGAZ protein is increased as compared to a plant expressing the corresponding wild type PGAZ protein.

[114] To determine the functionality of a specific PGAZ allele/protein in plants, particularly in Brassica plants, the level of resistance to pod drop in the plants can be determined by performing assays to determine the force required for detachment of the pods from the plants as described herein in the

Examples belowm, and/or by microscopic tests to examine, e.g., whether and how cells at the abscission zone of the pedicel of the pods are affected by mutations in PGAZ. The functionality of a specific PGAZ allele/protein can alternatively be evaluated by recombinant DNA techniques as known in the art, e.g., by expressing PGAZ in a host cell (e.g. a bacterium, such as E. coli) and evaluating e.g. substrate binding activity or in vitro catalysis of the hydrolysis of (l->4)-alpha-D-galactosiduronic linkages in galacturonans.

[115] Both endogenous and isolated nucleic acid sequences are provided herein. Also provided are fragments of the PGAZ sequences and PGAZ variant nucleic acid sequences defined above, for use as primers or probes and as components of kits according to another aspect of the invention (see further below). A "fragment" of a PGAZ or pgaz nucleic acid sequence or variant thereof (as defined) may be of various lengths, such as at least 10, 12, 15, 18, 20, 50, 100, 200, 500, 800, 1000, or 1500 contiguous nucleotides of the PGAZ or pgaz sequence (or of the variant sequence). Nucleic acid sequences encoding functional PGAZ proteins

[116] The nucleic acid sequences depicted in the sequence listing encode wild type, functional PGAZ proteins from Brassica napus, Brassica rapa, Brassica oleracea and Brassica nigra. Thus, these sequences are endogenous to the Brassica plants from which they were isolated. Other Brassica crop species, varieties, breeding lines or wild accessions may be screened for other PGAZ alleles, encoding the same PGAZ proteins or variants thereof. For example, nucleic acid hybridization techniques (e.g. Southern blot analysis, using for example stringent hybridization conditions) or PCR-based techniques may be used to identify PGAZ alleles endogenous to other Brassica plants, such as various Brassica napus varieties, lines or accessions, but also Brassica juncea (especially PGAZ alleles on the A- genome), Brassica carinata (especially PGAZ alleles on the C-genome) and Brassica rapa (A-genome) and Brassica oleracea (C-genome) plants, organs and tissues can be screened for other wild type PGAZ alleles. To screen such plants, plant organs or tissues for the presence of PGAZ alleles, the PGAZ nucleic acid sequences provided in the sequence listing, or variants or fragments of any of these, may be used. For example whole sequences or fragments may be used as probes or primers. For example specific or degenerate primers may be used to amplify nucleic acid sequences encoding PGAZ proteins from the genomic DNA of the plant, plant organ or tissue. These PGAZ nucleic acid sequences may be isolated and sequenced using standard molecular biology techniques. Bioinformatics analysis may then be used to characterize the allele(s), for example in order to determine which PGAZ allele the sequence corresponds to and which PGAZ protein or protein variant is encoded by the sequence. [11 ] Whether a nucleic acid sequence encodes a functional PGAZ protein can be analyzed by recombinant DNA techniques as known in the art, e.g., by a genetic complementation test using, e.g., an Arabidopsis plant, which is homozygous for a full knock-out pgaz mutant allele or a Brassica napus plant, which is homozygous for a full knock-out pgaz mutant allele of both the the PGAZ-A1, PGAZ- A2, PGAZ-C1 and/or the PGAZ-C2 gene. [118] In addition, it is understood that PGAZ nucleic acid sequences and variants thereof (or fragments of any of these) may be identified in silico, by screening nucleic acid databases for essentially similar sequences. Likewise, a nucleic acid sequence may be synthesized chemically. Fragments of nucleic acid molecules according to the invention are also provided, which are described further below.

Nucleic acid sequences encoding mutant PGAZ proteins [11 ] Nucleic acid sequences comprising one or more nucleotide deletions, insertions or substitutions relative to the wild type nucleic acid sequences are another embodiment of the invention, as are fragments of such mutant nucleic acid molecules. Such mutant nucleic acid sequences (referred to as pgaz sequences) can be generated and/or identified using various known methods, as described further below. Again, such nucleic acid molecules are provided both in endogenous form and in isolated form. In one embodiment, the mutation(s) result in one or more changes (deletions, insertions and/or substitutions) in the amino acid sequence of the encoded PGAZ protein (i.e. it is not a "silent mutation"). In another embodiment, the mutation(s) in the nucleic acid sequence result in a significantly reduced or completely abolished biological activity of the encoded PGAZ protein relative to the wild type protein. [120] The nucleic acid molecules may, thus, comprise one or more mutations, such as:

[121] (a) a "missense mutation", which is a change in the nucleic acid sequence that results in the substitution of an amino acid for another amino acid;

[122] (b) a "nonsense mutation" or "STOP codon mutation", which is a change in the nucleic acid sequence that results in the introduction of a premature STOP codon and thus the termination of translation (resulting in a truncated protein); plant genes contain the translation stop codons "TGA"

(UGA in RNA), "TAA" (UAA in RNA) and "TAG" (UAG in RNA); thus any nucleotide substitution, insertion, deletion which results in one of these codons to be in the mature mRNA being translated (in the reading frame) will terminate translation.

[123] (c) an "insertion mutation" of one or more amino acids, due to one or more codons having been added in the coding sequence of the nucleic acid;

[124] (d) a "deletion mutation" of one or more amino acids, due to one or more codons having been deleted in the coding sequence of the nucleic acid;

[125] (e) a "frameshift mutation", resulting in the nucleic acid sequence being translated in a different frame downstream of the mutation. A frameshift mutation can have various causes, such as the insertion, deletion or duplication of one or more nucleotides.

[126] As already mentioned, it is desired that the mutation(s) in the nucleic acid sequence preferably result in a mutant protein comprising significantly reduced or no biological activity in vivo or in the production of no protein Basically, any mutation which results in a protein comprising at least one amino acid insertion, deletion and/or substitution relative to the wild type protein can lead to

significantly reduced or no biological activity. It is, however, understood that mutations in certain parts of the protein are more likely to result in a reduced function of the mutant PGAZ protein, such as mutations leading to truncated proteins, whereby significant portions of the functional domains, such as the NTD motif, the DD motif, the GHG motif, and/or the RIK motif, are lacking.

[127] According to The Arabidopsis Information Resource (TAIR) database

(http://www.arabidopsis.org/), the Arabidopsis PGAZ protein (locus A t2g41850; SEQ ID NO: 3) is 433 amino acids in length. It comprises an NTD motif (substrate-binding region), comprising residues NTDG at positions 241-244 of SEQ ID NO: 3; a DD motif (catalytic region), comprising residues - -

GDDC at positions 263-266 of SEQ ID NO: 3; a GHG motif (catalytic region) comprising residues GHGISIGSLG at positions 286-295 of SEQ ID NO: 3, and a RIK motif (substrate-binding region) comprising residues RIK at positions 322-324 of SEQ ID NO: 3. Catalytic amino acids are the D at position 264 of SEQ ID NO: 3, and the H at position 287 of SEQ ID NO: 3 (Palanivelu, 2006, Indian J Biotechnol 5:148).

[128] The PGZ-A1 protein of Brassica napus (SEQ ID NO: 6 and 18) and of Brassica rapa (SEQ ID NO: 30), the PGAZ-C1 protein of Brassica napus (SEQ ID NOs: 12 and 24), and the PGAZ-B1 protein of Brassica nigra (SEQ ID NO: 42) described herein are about 433 amino acids in length and they comprise the NTD motif comprising residues NTDG at position 241-244; the DD motif comprising residues GDDC at positions 263-266; the GHG motif comprising residues GHGISIGSLG at positions 286-295; the RIK motif comprising residues RIK at positions 322-324, the catalytid amino acid D at position 264, and the catalytic amino acid H at position 287. The PGZ-A2 proteins of Brassica napus (SEQ ID NO: 9 and 21) described herein are about 408 amino acids in length and they comprise the NTD motif comprising residues NTDG at position 243-246; the DD motif comprising residues GDDC at positions 265-268; the GHG motif comprising residues GHGISIGSLG at positions 288-297; the RIK motif comprising residues RIK at positions 323-325, the catalytid amino acid D at position 266, and the catalytic amino acid H at position 289. The PGZ-C2 protein of Brassica napus (SEQ ID NO: 15 and 27) and of Brassica oleracea (SEQ ID NO: 39), and the the PGAZ-A2 protein of Brassica rapa (SEQ ID NO: 33) described herein are about 435 amino acids in length and they comprise the NTD motif comprising residues NTDG at position 243-246; the DD motif comprising residues GDDC at positions 265-268; the GHG motif comprising residues GHGISIGSLG at positions 288-297; the RIK motif comprising residues RIK at positions 323-325, the catalytid amino acid D at position 266, and the catalytic amino acid H at position 289. The PGAZ-C1 protein of Brassica oleracea (SEQ ID NO: 36) described herein is about 433 amino acids in length and they comprises the NTD motif comprising residues NTDG at position 243-246; the DD motif comprising residues GDDC at positions 265-268; the GHG motif comprising residues GHGISIGSLG at positions 288-297; the RIK motif comprising residues RIK at positions 323-325, the catalytid amino acid D at position 266, and the catalytic amino acid H at position 289. The PGAZ-B2 protein of Brassica nigra (SEQ ID NO: 45) described herein is about 434 amino acids in length and they comprises the NTD motif comprising residues NTDG at position 242- 245; the DD motif comprising residues GDDC at positions 264-267; the GHG motif comprising residues GHGISIGSLG at positions 287-296; the RIK motif comprising residues RIK at positions 322-324, the catalytid amino acid D at position 265, and the catalytic amino acid H at position 288.

[129] As described by Palanivelu, 2006 (Indian J Biotechnol 5:148) (incorporated herein by reference), the glycosidases use two highly conserved carboxtylic amino acids, Asp and His, to bring about hydrolysis of the susceptible glycosidic bond in sugar, whereby the His may act as as a proton donor and the Asp acts as a nucleophile. The conserved Asp (D) corresponds to D at position 264 of SEQ ID NO: 3 in the catalytic DD motif comprising residues GDDC at positions 263-266 of SEQ ID NO: 3; and the conserved His (H) corresponds to the H at position 287 of SEQ ID NO: 3 in the catalytic GHG motif comprising residues GHGISIGSLG at positions 286-295 of SEQ ID NO: 3. The conserved H is highly critical for catalytic activity. The NTD motif and the RIK motif are substrate binding regions. The NTD motif comprises residues NTDG at positions 241-244 of SEQ ID NO: 3, and the RIK motif comprises residues RIK at positions 322-324 of SEQ ID NO: 3.

[130] Table 1. Amino acid positions of the conserved motifs and catalytic residues in the Arabidopsis and Brassica PGAZ protein sequences. Numbers between brackets indicate amino acid positions in the respective sequences.

- -

[131] Optimal alignment of the Arabidopsis PGAZ nucleic acid (SEQ ID NOs: 1 and 2) and amino acid (SEQ ID NO: 3) sequences with PGAZ nucleic acid sequences, in particular the Brassica PGAZ nucleic acid and amino acid sequences of the present invention, allows to determine the positions of the corresponding conserved domains and amino acids in these Brassica sequences (see Table 1 for the Brassica PGAZ sequences of SEQ ID NOs: 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42 and 45).

[132] Thus in one embodiment, nucleic acid sequences comprising one or more of any of the types of mutations described above are provided. In another embodiment, pgaz sequences comprising one or more stop codon (nonsense) mutations, one or more missense mutations and/or one or more frameshift mutations are provided. Any of the above mutant nucleic acid sequences are provided per se (in isolated form), as are plants and plant parts comprising such sequences endogenously. In the tables herein below the most preferred pgaz alleles are described and seed deposits of Brassica napus seeds comprising one or more pgaz alleles have been deposited as indicated.

[133] A nonsense mutation in a PGAZ allele, as used herein, is a mutation in a PGAZ allele whereby one or more translation stop codons are introduced into the coding DNA and the corresponding mRNA sequence of the corresponding wild type PGAZ allele. Translation stop codons are TGA (UGA in the mRNA), TAA (UAA) and TAG (UAG). Thus, any mutation (deletion, insertion or substitution) that leads to the generation of an in- frame stop codon in the coding sequence will result in termination of translation and truncation of the amino acid chain. In one embodiment, a mutant PGAZ allele comprising a nonsense mutation is a PGAZ allele wherein an in- frame stop codon is introduced in the PGAZ codon sequence by a single nucleotide substitution, such as the mutation of CAG to TAG, TGG to TAG, TGG to TGA, or CAA to TAA. In another embodiment, a mutant PGAZ allele comprising a nonsense mutation is a PGAZ allele wherein an in- frame stop codon is introduced in the PGAZ codon sequence by double nucleotide substitutions, such as the mutation of CAG to TAA, TGG to TAA, or CGG to TAG or TGA. In yet another embodiment, a mutant PGAZ allele comprising a nonsense mutation is a PGAZ allele wherein an in- frame stop codon is introduced in the PGAZ codon sequence by triple nucleotide substitutions, such as the mutation of CGG to TAA. The truncated protein lacks the amino acids encoded by the coding DNA downstream of the mutation (i.e. the C-terminal part of the PGAZ protein) and maintains the amino acids encoded by the coding DNA upstream of the mutation (i.e. the N-terminal part of the PGAZ protein). In one embodiment, a mutant PGAZ allele comprising a nonsense mutation is a PGAZ allele wherein the nonsense mutation is present anywhere in front of the conserved RIK motif at positions 321-323 of SEQ ID NO: 3, so that at least the conserved RIK domain is lacking. The more truncated the mutant PGAZ protein is in comparison to the wild type PGAZ protein, the more the truncation may result in a significantly reduced or no activity of the PGAZ protein. Thus in another embodiment, a mutant PGAZ allele comprising a nonsense mutation which results in a truncated protein of less than about 287, or 286, or 288, or 289 amino acids (lacking the catalytic H), less than about 286, or 285, or 287, or 288 amino acids (lacking the conserved GHG motif), less than about 264, or 263, or 265, or 266 amino acids (lacking the catalytic D), less than about 263, or 262, or 264, or 265 amino acids (lacking the comserved DD motif), less than about 241, or 240, or 242, or 243 amino acids (lacking the conserved NTD motif), or even less amino acids in length. [134] It will be clear as described herein in the examples that the PGAZ alleles that are truncated at a position corresponding to position 274 of SEQ ID NO: 3 (PGAZ-A1 -EMS03 and PGAZ-A2-EMS08), lacking the GHG motif, the RIK motif, and the catalytic H, which are the longest truncated PGAZ proteins of the Examples, contribute to an increase of pod drop resistance. Therefore, in a particular embodiment, the PGAZ allele according to the invention encodes a truncated protein lacking the GHG motif, the RIK motif, and the catalytic H.

[135] Obviously, mutations are not limited to the ones indicated above and it is understood that analogous STOP mutations may be present in pgaz alleles other than those depicted in the sequence listing and referred to in the tables above.

[136] A missense mutation in a PGAZ allele, as used herein, is any mutation (deletion, insertion or substitution) in a PGAZ allele whereby one or more codons are changed into the coding DNA and the corresponding mRNA sequence of the corresponding wild type PGAZ allele, resulting in the substitution of one or more amino acids in the wild type PGAZ protein for one or more other amino acids in the mutant PGAZ protein. In one embodiment, a mutant PGAZ allele comprising a missense mutation is a PGAZ allele wherein one or more of the conserved amino acids indicated above or in Table 1 is/are substituted. Missense mutations which result in the substitution of, e.g., the amino acid at a position corresponding to position 264 or 287 of SEQ ID NO: 3 are more likely to result in a significantly reduced or no activity, due to a reduced catalytic activity of the PGAZ protein. Similarly missense mutations which result in the substitution of, e.g., the amino acids in the NTDG motif at a position corresponding to position 241, 242, 243 or 244 of SEQ ID NO: 3, of the DD motif at a position corresponding to position 263, 265 or 266 of SEQ ID NO: 3, of the GHG motif at a position corresponding to position 286, 288, 289, 290, 291, 292, 293, 294, or 295 of SEQ ID NO: 3, or of the RIK motif at a position corresponding to position 321, 322 or 323 of SEQ ID NO: 3 are more likely to result in a significantly reduced or no activity.

[137] A frameshift mutation in a PGAZ allele, as used herein, is a mutation (deletion, insertion, duplication, and the like) in a PGAZ allele that results in the nucleic acid sequence being translated in a different frame downstream of the mutation. In one embodiment, a mutant PGAZ allele comprising a frameshift mutation is a PGAZ allele comprising a frameshift mutation upstream of the codon encoding the first amino acid of the NTD motif corresponding to position 241 of SEQ ID NO: 3, or comprising a frameshift mutation upstream of the codon encoding the first amino acid of the DD motif corresponding to position 263 of SEQ ID NO: 3, or comprising a frameshift mutation upstream of the codon encoding - 5 - the first amino acid of the GHG motif corresponding to position 286 of SEQ ID NO: 3, or comprising a frameshift mutation upstream of the codon encoding the first amino acid of the RIK motif corresponding to position 321 of SEQ ID NO: 3, or comprising a frameshift mutation upstream of the codon encoding the catalytic D corresponding to position 264 of SEQ ID NO: 3, or comprising a frameshift mutation upstream of the codon encoding the catalytic H corresponding to position 287 of SEQ ID NO: 3.

[138] A mutant PGAZ allele may also be a PGAZ allele which produces no PGAZ protein. Examples of mutant alleles that do not produce a protein are alleles having mutations leading to no production or degradation of the mRNA, such as mutations in promoter regions abolishing mRNA production, stop codon mutations leading to degradation of the mRNA (nonsense-mediated decay; see, for example, Baker and Parker, 2004, Curr Opin Cell Biol 16:293), splice site mutations leading to RNA degradation (see, for example, Isken and Maquat, 2007, Genes Dev 21 : 1833), or mutations in the protein coding sequence comprising mutation or deletion of the ATG start codon, such that no protein is produced, or gross deletions in the gene leading to absence of (part of) the protein coding sequence.

[139] The mutant PGAZ alleles according to the invention can thus comprise nucleotide sequences which comprise at least 90% but less than 100% sequence identity to SEQ ID NO: 1 , SEQ ID NO: 4, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 13, SEQ ID NO: 16, SEQ ID NO: 19, SEQ ID NO: 22, SEQ ID NO: 25, SEQ ID NO: 28, SEQ ID NO: 31, SEQ ID NO: 34, SEQ ID NO: 37, SEQ ID NO: 40, or SEQ ID NO: 43; or can comprise nucleotide sequences comprising a coding sequence which comprises at at least 90% but less than 100% sequence identity to SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 8, SEQ ID NO: 11, SEQ ID NO: 14, SEQ ID NO: 17, SEQ ID NO: 20, SEQ ID NO: 23, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 32, SEQ ID NO: 35, SEQ ID NO: 38, SEQ ID NO: 41, or SEQ ID NO: 44; or can comprise nucleotide sequences encoding an amino acid sequence which comprises at least 90% but less than 100% sequence identity to SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 12, SEQ ID NO: 15, SEQ ID NO: 18, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 27, SEQ ID NO: 30, SEQ ID NO: 33, SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, or SEQ ID NO: 45. Said at least 90% can be at least 90%, or at least 93%, or at least 95%, or at least 96%, or at least 97%), or at least 98%, or 99%. However, the mutant PGAZ alleles according to the invention can not comprise nucleotide sequences comprising 100%> sequence identity to the above sequences.

Furthermore, the mutant PGAZ alleles according to the invention can comprise sequence identity which is lower than 90%) to the above-mentioned sequences, such as, for example, when part or all of the wild type PGAZ gene is deleted. In such a case, a mutant PGAZ allele may also refer to a genetic locus corresponding to the genetic locus of a wild type PGAZ allele, wherein a PGAZ allele is present having less than 100%) sequence identity to the wild type allele, or wherein a part of, or the complete PGAZ gene, is deleted. - -

[140] Also provided herein is a chimeric gene comprising the following operably linked DNA fragments: (a) a plant-expressible promoter; (b) a DNA region, which when transcribed yields an RNA or protein molecule inhibitory to one or more PGAZ genes; and, optionally (c) a 3' end region involved in transcription termination and polyadenylation. Said RNA molecule inhibitory to one or more PGAZ gene can be RNA molecules as described herein.

[141] As used herein, the term "plant-expressible promoter" means a DNA sequence that is capable of controlling (initiating) transcription in a plant cell. This includes any promoter of plant origin, but also any promoter of non-plant origin which is capable of directing transcription in a plant cell, i.e., certain promoters of viral or bacterial origin such as the CaMV35S (Harpster et al. (1988) Mol Gen Genet. 212(1):182-90, the subterranean clover virus promoter No 4 or No 7 (WO9606932), or T-DNA gene promoters. Suitable promoters for the invention are constitutive plant-expressible promoters.

Constitutive plant-expressible promoters are well known in the art, and include the CaMV35S promoter (Harpster et al. (1988) Mol Gen Genet. 212(1): 182-90), Actin promoters, such as, for example, the promoter from the Rice Actin gene (McElroy et al., 1990, Plant Cell 2:163), the promoter of the Cassava Vein Mosaic Virus (Verdaguer et al., 1996 Plant Mol. Biol. 31 : 1129), the GOS promoter (de Pater et al., 1992, Plant J. 2:837), the Histone H3 promoter (Chaubet et al., 1986, Plant Mol Biol 6:253), the Agrobacterium tumefaciens Nopaline Synthase (Nos) promoter (Depicker et al., 1982, J. Mol. Appl. Genet. 1 : 561), or Ubiquitin promoters, such as, for example, the promoter of the maize Ubiquitin-1 gene (Christensen et al., 1992, Plant Mol. Biol. 18:675). Also suitable are promoters that dreve expression specifically or preferentially in the abscission zone, preferably the pod pedicel abscission zone.

[142] A "transcription termination and polyadenylation region" as used herein is a sequence that drives the cleavage of the nascent RNA, whereafter a poly(A) tail is added at the resulting RNA 3 ' end, functional in plant cells. Transcription termination and polyadenylation signals functional in plant cells include, but are not limited to, 3'nos, 3'35S, 3'his and 3'g7.

Amino acid sequences according to the invention

[143] Provided are both wild type (functional) PGAZ amino acid sequences and mutant PGAZ amino acid sequences (comprising one or more mutations, preferably mutations which result in a significantly reduced or no biological activity of the PGAZ protein) from Brassicaceae, particularly from Brassica species, especially from Brassica napus, Brassica rapa, Brassica oleracea and Brassica nigra, but also from other Brassica crop species. For example, Brassica species comprising an A and/or a C genome may encode different PGAZ-A or PGAZ -C amino acids. In addition, mutagenesis or gene targeting methods can be used to generate mutations in wild type PGAZ alleles, thereby generating mutant alleles _? which can encode further mutant PGAZ proteins. In one embodiment the wild type and/or mutant PGAZ amino acid sequences are provided within a Brassica plant (i.e. endogenously). However, isolated PGAZ amino acid sequences (e.g. isolated from the plant or made synthetically), as well as variants thereof and fragments of any of these are also provided herein. [1 4] A significantly reduced or no biological activity of the PGAZ protein can be a reduction of at least 10%, or of at least 20%, or of at least 40%, or of at least 60%, or of at least 80%, or of at least 90%, or of at least 95%, or of at least 98%, or a reduction of 100%) in which no protein activity can be detected, as compared to a functional PGAZ protein, such as a functional PGAZ protein encoded by a wild type PGAZ allele. PGAZ activity can be determined, for example, as described by Torres et al, 2011, Enzyme and Microbial Technology 48: 123 (incorporated herein by reference).

[145] Amino acid sequences of PGAZ proteins have been isolated from Brassica napus, Brassica rapa, Brassica oleracea and Brassica nigra as depicted in the sequence listing. The wild type PGAZ sequences are depicted, while the mutant PGAZ sequences of these sequences, and of sequences essentially similar to these, are described herein below, with reference to the wild type PGAZ sequences. [146] As described above, the PGAZ proteins of Brassica described herein are about 4 amino acids in length and comprise a number of structural and functional domains.

[147] "PGAZ-A1 amino acid sequences" or "PGAZ-A1 variant amino acid sequences" according to the invention are amino acid sequences having at least 75%), at least 80%), at least 85%), at least 90%), at least 95%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs 6, 18, and 30. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[148] "PGAZ-A2 amino acid sequences" or "PGAZ-A2 variant amino acid sequences" according to the invention are amino acid sequences having at least 75%), at least 80%), at least 85%), at least 90%), at least 95%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs 9, 21, and 33. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" to the PGAZ sequences provided in the sequence listing.

[149] "PGAZ-C1 amino acid sequences" or "PGAZ-C1 variant amino acid sequences" according to the invention are amino acid sequences having at least 75%), at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs 12, 24, and 36. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[150] "PGAZ-C2 amino acid sequences" or "PGAZ-C2 variant amino acid sequences" according to the invention are amino acid sequences having at least 75%), at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with any one of SEQ ID NOs 15, 27, and 39. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[151] "PGAZ-B 1 amino acid sequences" or "PGAZ-B 1 variant amino acid sequences" or "BniPGAZ- B 1 amino acid sequences" or "PGAZ-B 1 amino acid sequences from Brassica nigra" or "Brassica nigra PGAZ-B 1 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99%) or 100%) sequence identity with SEQ ID NO: 42. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[152] "PGAZ-B2 amino acid sequences" or "PGAZ-B2 variant amino acid sequences" or "BniPGAZ- B2 amino acid sequences" or "PGAZ-B2 amino acid sequences from Brassica nigra" or "Brassica nigra PGAZ-B2 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%, 98%, 99%) or 100%) sequence identity with SEQ ID NO: 45. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[153] "BnPGAZ-Al amino acid sequences" or "PGAZ-A1 amino acid sequences from Brassica napus" or "Brassica napus PGAZ-A1 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 15%, at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NOs 6 or 18. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[154] "BnPGAZ-A2 amino acid sequences" or "PGAZ- A2 amino acid sequences from Brassica napus" or "Brassica napus PGAZ- A2 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%), at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NOs 9 or 21. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing. [155] "BnPGAZ-Cl amino acid sequences" or "PGAZ- CI amino acid sequences from Brassica napus" or "Brassica napus PGAZ- CI amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%), at least 80%), at least 85%), at least 90%), at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NOs 12 or 24. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[156] "BnPGAZ-C2 amino acid sequences" or "PGAZ- C2 amino acid sequences from Brassica napus" or "Brassica napus PGAZ- C2 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%, at least 80%, at least 85%, at least 90%>, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NOs 15 or 27. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[157] "BrPGAZ-Al amino acid sequences" or "PGAZ-A1 amino acid sequences from Brassica rapa" or "Brassica rapa PGAZ-A1 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 96%, 97%o, 98%o, 99%o or 100%> sequence identity with SEQ ID NO: 30. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing. [158] "BrPGAZ-A2 amino acid sequences" or "PGAZ- A2 amino acid sequences from Brassica rapa" or "Brassica rapa PGAZ- A2 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%>, at least 80%, at least 85%>, at least 90%, at least 95%>, 96%, 97%o, 98%), 99%) or 100%> sequence identity with SEQ ID NO: 33. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[159] "BoPGAZ-Cl amino acid sequences" or "PGAZ- CI amino acid sequences from Brassica oleracea" or "Brassica oleracea PGAZ- CI amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%>, at least 80%, at least 85%>, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 36. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[160] "BoPGAZ-C2 amino acid sequences" or "PGAZ- C2 amino acid sequences from Brassica oleracea" or "Brassica oleracea PGAZ- C2 amino acid sequences" or variants thereof according to the invention are amino acid sequences having at least 75%>, at least 80%, at least 85%>, at least 90%, at least 95%, 96%, 97%, 98%, 99% or 100% sequence identity with SEQ ID NO: 39. These amino acid sequences may also be referred to as being "essentially similar" or "essentially identical" the PGAZ sequences provided in the sequence listing.

[161] Thus, the invention provides both amino acid sequences of wild type, functional PGAZ proteins, including variants and fragments thereof (as defined further below), as well as mutant amino acid - - sequences of any of these, whereby the mutation in the amino acid sequence preferably results in a significant reduction in or a complete abolishment of the biological activity of the PGAZ protein as compared to the biological activity of the corresponding wild type PGAZ protein. A significant reduction in or complete abolishment of the biological activity of the PGAZ protein refers herein to a reduction in or abolishment of the substrate binding activity or the catalytic activity, such that the pod drop resistance of a plant expressing the mutant PGAZ protein is increased as compared to a plant expressing the corresponding wild type PGAZ protein compared to the pod drop resistance of a corresponding wild type plant.

[162] Both endogenous and isolated amino acid sequences are provided herein. Also provided are fragments of the PGAZ amino acid sequences and PGAZ variant amino acid sequences defined above. A "fragment" of a PGAZ amino acid sequence or variant thereof (as defined) may be of various lengths, such as at least 10, 12, 15, 18, 20, 50, 100, 150, 175, 200, 150, 300, 350 or 400 contiguous amino acids of the PGAZ sequence (or of the variant sequence).

Amino acid sequences of functional PGAZ proteins

[163] The amino acid sequences depicted in the sequence listing are wild type, functional PGAZ proteins from Brassica napus, Brassica rapa, Brassica oleracea and Brassica nigra. Thus, these sequences are endogenous to the Brassica plants from which they were isolated. Other Brassica crop species, varieties, breeding lines or wild accessions may be screened for other functional PGAZ proteins with the same amino acid sequences or variants thereof, as described above. [164] In addition, it is understood that PGAZ amino acid sequences and variants thereof (or fragments of any of these) may be identified in silico, by screening amino acid databases for essentially similar sequences. Fragments of amino acid molecules according to the invention are also provided.

Amino acid sequences of mutant PGAZ proteins

[165] Amino acid sequences comprising one or more amino acid deletions, insertions or substitutions relative to the wild type amino acid sequences are another embodiment of the invention, as are fragments of such mutant amino acid molecules. Such mutant amino acid sequences can be generated and/or identified using various known methods, as described above. Again, such amino acid molecules are provided both in endogenous form and in isolated form.

[166] In one embodiment, the mutation(s) in the amino acid sequence result in a significantly reduced or completely abolished biological activity of the PGAZ protein relative to the wild type protein. As described above, basically, any mutation which results in a protein comprising at least one amino acid insertion, deletion and/or substitution relative to the wild type protein can lead to significantly reduced or no biological activity. It is, however, understood that mutations in certain parts of the protein are more likely to result in a reduced function of the mutant PGAZ protein, such as mutations leading to truncated proteins, whereby significant portions of the conserved domains, such as the NTD motif, the DD motif, the GHG motif, the RIK motif, or the catalytic D or the catalytic H are lacking or being substituted.

[167] Thus in one embodiment, mutant PGAZ proteins are provided comprising one or more deletion or insertion mutations, whereby the deletion(s) or insertion(s) result(s) in a mutant protein which has significantly reduced or no activity in vivo. Such mutant PGAZ proteins are PGAZ proteins wherein at least 1, at least 2, 3, 4, 5, 10, 20, 30, 50, 100, 100, 150, 175, 180, 200, 250, 300, 350, 400 or more amino acids are deleted or inserted as compared to the wild type PGAZ protein, whereby the deletion(s) or insertion(s) result(s) in a mutant protein which has significantly reduced or no activity in vivo. [168] In another embodiment, mutant PGAZ proteins are provided which are truncated whereby the truncation results in a mutant protein that has significantly reduced or no activity in vivo. Such truncated PGAZ proteins are PGAZ proteins which lack functional domains in the C-terminal part of the corresponding wild type PGAZ protein and which maintain the N-terminal part of the corresponding wild type PGAZ protein. Thus in one embodiment, a truncated PGAZ protein comprising the N-terminal part of the corresponding wild type PGAZ protein up to but not including the first conserved G residue of the GHG motif (at a position corresponding to position 286 of SEQ ID NO: 3) is provided. The more truncated the mutant protein is in comparison to the wild type protein, the more the truncation may result in a significantly reduced or no activity of the PGAZ protein. Thus in another embodiment, a truncated PGAZ protein comprising the N-terminal part of the corresponding wild type PGAZ protein lacking part or all of the RIK motif, and/or lacking part or all of the GHG motif, and/or lacking the catalytic H, and/or lacking part or all of DD motif, and/or lacking the catalytic D, and/or lacking part or all of NTD motif (as described above), or even more amino acids are provided.

[169] In yet another embodiment, mutant PGAZ proteins are provided comprising one or more substitution mutations, whereby the substitution(s) result(s) in a mutant protein that has significantly reduced or no activity in vivo. Such mutant PGAZ proteins are PGAZ proteins whereby conserved amino acid residues which have a specific function, substrate binding or a catalytic function are substituted. Thus in one embodiment, a mutant PGAZ protein comprising a substitution of a conserved amino acid residue which has a biological function, such as the conserved amino acids of the NTD motif, the DD motif, the GHG motif, the RIK motif, or of the catalytid D, or of the catalytic H, is provided.

Methods according to the invention

[170] Mutant pgaz alleles may be generated (for example induced by mutagenesis or gene targeting) and/or identified using a range of methods, which are conventional in the art, for example using PCR based methods to amplify part or all of the pgaz genomic or cDNA. - -

[171] Following mutagenesis, plants are grown from the treated seeds, or regenerated from the treated cells using known techniques. For instance, mutagenized seeds may be planted in accordance with conventional growing procedures and following self-pollination seed is formed on the plants.

Alternatively, doubled haploid plantlets may be extracted from treated microspore or pollen cells to immediately form homozygous plants, for example as described by Coventry et al. (1988, Manual for Microspore Culture Technique for Brassica napus. Dep. Crop Sci. Techn. Bull. OAC Publication 0489. Univ. of Guelph, Guelph, Ontario, Canada). Additional seed which is formed as a result of such self-pollination in the present or a subsequent generation may be harvested and screened for the presence of mutant PGAZ alleles, using techniques which are conventional in the art, for example polymerase chain reaction (PCR) based techniques (amplification of the pgaz alleles) or hybridization based techniques, e.g. Southern blot analysis, BAC library screening, and the like, and/or direct sequencing of pgaz alleles. To screen for the presence of point mutations (so called Single Nucleotide Polymorphisms or SNPs) in mutant PGAZ alleles, SNP detection methods conventional in the art can be used, for example oligoligation-based techniques, single base extension-based techniques or techniques based on differences in restriction sites, such as TILLING.

[172] As described above, mutagenization (spontaneous as well as induced) of a specific wild-type PGAZ allele results in the presence of one or more deleted, inserted, or substituted nucleotides

(hereinafter called "mutation region") in the resulting mutant PGAZ allele. The mutant PGAZ allele can thus be characterized by the location and the configuration of the one or more deleted, inserted, or substituted nucleotides in the wild type PGAZ allele. The site in the wild type PGAZ allele where the one or more nucleotides have been inserted, deleted, or substituted, respectively, is herein also referred to as the "mutation region or sequence". A "5' or 3' flanking region or sequence" as used herein refers to a DNA region or sequence in the mutant (or the corresponding wild type) PGAZ allele of at least 20 bp, preferably at least 50 bp, at least 750 bp, at least 1500 bp, and up to 5000 bp of DNA different from the DNA containing the one or more deleted, inserted, or substituted nucleotides, preferably DNA from the mutant (or the corresponding wild type) PGAZ allele which is located either immediately upstream of and contiguous with (5' flanking region or sequence") or immediately downstream of and contiguous with (3 ' flanking region or sequence") the mutation region in the mutant PGAZ allele (or in the corresponding wild type PGAZ allele). A "joining region" as used herein refers to a DNA region in the mutant (or the corresponding wild type) PGAZ allele where the mutation region and the 5' or 3' flanking region are linked to each other. A "sequence spanning the joining region between the mutation region and the 5' or 3' flanking region thus comprises a mutation sequence as well as the flanking sequence contiguous therewith.

[173] The tools developed to identify a specific mutant PGAZ allele or the plant or plant material comprising a specific mutant PGAZ allele, or products which comprise plant material comprising a specific mutant PGAZ allele are based on the specific genomic characteristics of the specific mutant PGAZ allele as compared to the genomic characteristics of the corresponding wild type PGAZ allele, such as, a specific restriction map of the genomic region comprising the mutation region, molecular markers or the sequence of the flanking and/or mutation regions.

[174] Once a specific mutant PGAZ allele has been sequenced, primers and probes can be developed which specifically recognize a sequence within the 5' flanking, 3' flanking and/or mutation regions of the mutant PGAZ allele in the nucleic acid (DNA or RNA) of a sample by way of a molecular biological technique. For instance a PCR method can be developed to identify the mutant PGAZ allele in biological samples (such as samples of plants, plant material or products comprising plant material). Such a PCR is based on at least two specific "primers": one recognizing a sequence within the 5' or 3' flanking region of the mutant PGAZ allele and the other recognizing a sequence within the 3' or 5' flanking region of the mutant PGAZ allele, respectively; or one recognizing a sequence within the 5' or 3' flanking region of the mutant PGAZ allele and the other recognizing a sequence within the mutation region of the mutant PGAZ allele; or one recognizing a sequence within the 5' or 3' flanking region of the mutant PGAZ allele and the other recognizing a sequence spanning the j oining region between the 3 ' or 5 ' flanking region and the mutation region of the specific mutant PGAZ allele (as described further below), respectively.

[175] A suitable method for identifying a mutant PGAZ allele according to the invention is a method comprising comprises subjecting the biological sample to an amplification reaction assay using a set of at least two primers, said set being selected from the group consisting of:

(a) a set of primers, wherein one of said primers specifically recognizes the 5' or 3' flanking region of the mutant PGAZ allele and the other of said primers specifically recognizes the mutation region of the mutant PGAZ allele, and

(b) a set of primers, wherein one of said primers specifically recognizes the 5' or 3' flanking region of the mutant PGAZ allele and the other of said primers specifically recognizes the joining region between the 3' or 5' flanking region and the mutation region of the mutant

PGAZ allele, respectively.

[176] The primers preferably have a sequence of between 15 and 35 nucleotides which under optimized PCR conditions "specifically recognize" a sequence within the 5' or 3' flanking region, a sequence within the mutation region, or a sequence spanning the joining region between the 3' or 5' flanking and mutation regions of the specific mutant PGAZ allele, so that a specific fragment ("mutant PGAZ specific fragment" or discriminating amplicon) is amplified from a nucleic acid sample comprising the specific mutant PGAZ allele. This means that only the targeted mutant PGAZ allele, and no other sequence in the plant genome, is amplified under optimized PCR conditions.

[177] PCR primers suitable for the invention may be the following: - oligonucleotides ranging in length from 17 nt to about 200 nt, comprising a nucleotide sequence of at least 17 consecutive nucleotides, preferably 20 consecutive nucleotides selected from the 5' or 3' flanking sequence of a specific mutant PGAZ allele or the complement thereof (i.e., for example, the sequence 5' or 3' flanking the one or more nucleotides deleted, inserted or substituted in the mutant PGAZ alleles of the invention, such as the sequence 5' or 3' flanking the non-sense, mis-sense or frameshift mutations described above or the sequence 5' or 3' flanking the STOP codon mutations indicated in the above Tables or the substitution mutations indicated above or the complement thereof) (primers recognizing 5' flanking sequences); or

- oligonucleotides ranging in length from 17 nt to about 200 nt, comprising a nucleotide sequence of at least 17 consecutive nucleotides, preferably 20 nucleotides selected from the sequence of the mutation region of a specific mutant PGAZ allele or the complement thereof (i.e., for example, the sequence of nucleotides inserted or substituted in the PGAZ genes of the invention or the complement thereof) (primers recognizing mutation sequences).

[178] The primers may of course be longer than the mentioned 17 consecutive nucleotides, and may e.g. be 18, 19, 20, 21, 30, 35, 50, 75, 100, 150, 200 nt long or even longer. The primers may entirely consist of nucleotide sequence selected from the mentioned nucleotide sequences of flanking and mutation sequences. However, the nucleotide sequence of the primers at their 5' end (i.e. outside of the 3 '-located 17 consecutive nucleotides) is less critical. Thus, the 5' sequence of the primers may consist of a nucleotide sequence selected from the flanking or mutation sequences, as appropriate, but may contain several (e.g. 1, 2, 5, 10) mismatches. The 5' sequence of the primers may even entirely consist of a nucleotide sequence unrelated to the flanking or mutation sequences, such as e.g. a nucleotide sequence representing restriction enzyme recognition sites. Such unrelated sequences or flanking DNA sequences with mismatches should preferably be not longer than 100, more preferably not longer than 50 or even 25 nucleotides. [179] Moreover, suitable primers may comprise or consist of a nucleotide sequence spanning the joining region between flanking and mutation sequences (i.e., for example, the joining region between a sequence 5' or 3' flanking one or more nucleotides deleted, inserted or substituted in the mutant PGAZ alleles of the invention and the sequence of the one or more nucleotides inserted or substituted or the sequence 3' or 5', respectively, flanking the one or more nucleotides deleted, such as the joining region between a sequence 5' or 3' flanking non-sense, missense or frameshift mutations in the PGAZ genes of the invention described above and the sequence of the non-sense, missense or frameshift mutations, or the joining region between a sequence 5' or 3' flanking a potential STOP codon mutation as indicated in the above Tables or the substitution mutations indicated above and the sequence of the potential STOP codon mutation or the substitution mutations, respectively), provided the nucleotide sequence is not derived exclusively from either the mutation region or flanking regions. ₅

[180] It will also be immediately clear to the skilled artisan that properly selected PCR primer pairs should also not comprise sequences complementary to each other.

[181] For the purpose of the invention, the "complement of a nucleotide sequence represented in SEQ ID No: X" is the nucleotide sequence which can be derived from the represented nucleotide sequence by replacing the nucleotides through their complementary nucleotide according to Chargaff s rules (A ->T; G ->C) and reading the sequence in the 5' to 3' direction, i.e. in opposite direction of the represented nucleotide sequence.

[182] Examples of primers suitable to identify specific mutant PGAZ alleles are described in the Examples. [183] As used herein, "the nucleotide sequence of SEQ ID No. Z from position X to position Y" indicates the nucleotide sequence including both nucleotide endpoints.

[184] Preferably, the amplified fragment has a length of between 50 and 1000 nucleotides, such as a length between 50 and 500 nucleotides, or a length between 100 and 350 nucleotides. The specific primers may have a sequence which is between 80 and 100% identical to a sequence within the 5' or 3' flanking region, to a sequence within the mutation region, or to a sequence spanning the joining region between the 3' or 5' flanking and mutation regions of the specific mutant PGAZ allele, provided the mismatches still allow specific identification of the specific mutant PGAZ allele with these primers under optimized PCR conditions. The range of allowable mismatches however, can easily be determined experimentally and are known to a person skilled in the art. [185] Detection and/or identification of a "mutant PGAZ specific fragment" can occur in various ways, e.g., via size estimation after gel or capillary electrophoresis or via fluorescence-based detection methods. The mutant PGAZ specific fragments may also be directly sequenced. Other sequence specific methods for detection of amplified DNA fragments are also known in the art.

[186] Standard PCR protocols are described in the art, such as in 'PCR Applications Manual" (Roche Molecular Biochemicals, 3rd Edition, 2006) and other references. The optimal conditions for the PCR, including the sequence of the specific primers, is specified in a "PCR identification protocol" for each specific mutant PGAZ allele. It is however understood that a number of parameters in the PCR identification protocol may need to be adjusted to specific laboratory conditions, and may be modified slightly to obtain similar results. For instance, use of a different method for preparation of DNA may require adjustment of, for instance, the amount of primers, polymerase, MgCb concentration or annealing conditions used. Similarly, the selection of other primers may dictate other optimal conditions for the PCR identification protocol. These adjustments will however be apparent to a person skilled in the art, and are furthermore detailed in current PCR application manuals such as the one cited above. [187] Examples of PCR identification protocols to identify specific mutant PGAZ alleles are described in the Examples.

[188] Alternatively, specific primers can be used to amplify a mutant PGAZ specific fragment that can be used as a "specific probe" for identifying a specific mutant PGAZ allele in biological samples.

Contacting nucleic acid of a biological sample, with the probe, under conditions that allow hybridization of the probe with its corresponding fragment in the nucleic acid, results in the formation of a nucleic acid/probe hybrid. The formation of this hybrid can be detected (e.g. labeling of the nucleic acid or probe), whereby the formation of this hybrid indicates the presence of the specific mutant PGAZ allele. Such identification methods based on hybridization with a specific probe (either on a solid phase carrier or in solution) have been described in the art. The specific probe is preferably a sequence that, under optimized conditions, hybridizes specifically to a region within the 5' or 3' flanking region and/or within the mutation region of the specific mutant PGAZ allele (hereinafter referred to as "mutant PGAZ specific region"). Preferably, the specific probe comprises a sequence of between 10 and 1000 bp, 50 and 600 bp, between 100 to 500 bp, between 150 to 350bp, which is at least 80%, preferably between 80 and 85%o, more preferably between 85 and 90%>, especially preferably between 90 and 95%, most preferably between 95% and 100%> identical (or complementary) to the nucleotide sequence of a specific region. Preferably, the specific probe will comprise a sequence of about 13 to about 100 contiguous nucleotides identical (or complementary) to a specific region of the specific mutant PGAZ allele.

[189] A suitable method for identifying a mutant PGAZ allele is a method comprising subjecting the biological sample to a hybridization assay using at least one specific probe, said probe being selected from the group consisting of:

(a) a probe specifically recognizing the mutation region of the mutant PGAZ allele, and

(b) a probe specifically recognizing the joining region between the 3' or 5' flanking region between the mutation region of the mutant PGAZ allele. [190] Specific probes suitable for the invention may be the following:

- oligonucleotides ranging in length from 13 nt to about 1000 nt, comprising a nucleotide sequence of at least 13 consecutive nucleotides selected from the 5' or 3' flanking sequence of a specific mutant PGAZ allele or the complement thereof (i.e., for example, the sequence 5' or 3' flanking the one or more nucleotides deleted, inserted or substituted in the mutant PGAZ alleles of the invention, such as the sequence 5' or 3' flanking the non-sense, mis-sense or frameshift mutations described above or the sequence 5' or 3' flanking the potential STOP codon mutations indicated in the above Tables or the substitution mutations indicated above), or a sequence having at least 80% sequence identity therewith (probes recognizing 5' flanking sequences); or

- oligonucleotides ranging in length from 13 nt to about 1000 nt, comprising a nucleotide sequence of at least 13 consecutive nucleotides selected from the mutation sequence of a specific mutant PGAZ allele or the complement thereof (i.e., for example, the sequence of nucleotides inserted or substituted _? in the PGAZ genes of the invention, or the complement thereof), or a sequence having at least 80% sequence identity therewith (probes recognizing mutation sequences).

[191] The probes may entirely consist of nucleotide sequence selected from the mentioned nucleotide sequences of flanking and mutation sequences. However, the nucleotide sequence of the probes at their 5' or 3' ends is less critical. Thus, the 5' or 3' sequences of the probes may consist of a nucleotide sequence selected from the flanking or mutation sequences, as appropriate, but may consist of a nucleotide sequence unrelated to the flanking or mutation sequences. Such unrelated sequences should preferably be not longer than 50, more preferably not longer than 25 or even not longer than 20 or 15 nucleotides. [1 2] Moreover, suitable probes may comprise or consist of a nucleotide sequence spanning the joining region between flanking and mutation sequences (i.e., for example, the joining region between a sequence 5' or 3' flanking one or more nucleotides deleted, inserted or substituted in the mutant PGAZ alleles of the invention and the sequence of the one or more nucleotides inserted or substituted or the sequence 3' or 5', respectively, flanking the one or more nucleotides deleted, such as the joining region between a sequence 5' or 3' flanking non-sense, mis-sense or firameshift mutations in the PGAZ genes of the invention described above and the sequence of the non-sense, mis-sense or firameshift mutations, or the joining region between a sequence 5' or 3' flanking a potential STOP codon mutation as indicated in the above Tables or the substitution mutations indicated above and the sequence of the potential STOP codon or substitution mutation, respectively), provided the mentioned nucleotide sequence is not derived exclusively from either the mutation region or flanking regions.

[193] Examples of specific probes suitable to identify specific mutant PGAZ alleles are described in the Examples.

[194] Detection and/or identification of a "mutant PGAZ specific region" hybridizing to a specific probe can occur in various ways, e.g., via size estimation after gel electrophoresis or via fluorescence- based detection methods. Other sequence specific methods for detection of a "mutant PGAZ specific region" hybridizing to a specific probe are also known in the art.

[195] Alternatively, plants or plant parts comprising one or more mutant pgaz alleles can be generated and identified using other methods, such as the "Delete-a-gene™" method which uses PCR to screen for deletion mutants generated by fast neutron mutagenesis (reviewed by Li and Zhang, 2002, Funct Integr Genomics 2:254-258), by the TILLING (Targeting Induced Local Lesions IN Genomes) method which identifies EMS-induced point mutations using denaturing high-performance liquid chromatography (DHPLC) to detect base pair changes by heteroduplex analysis (McCallum et al. , 2000, Nat Biotech 18:455, and McCallum et al. 2000, Plant Physiol. 123, 439-442), etc. As mentioned, TILLING uses high-throughput screening for mutations (e.g. using Cel 1 cleavage of mutant- wildtype DNA heteroduplexes and detection using a sequencing gel system). Thus, the use of TILLING to identify plants or plant parts comprising one or more mutant pgaz alleles and methods for generating and identifying such plants, plant organs, tissues and seeds is encompassed herein. Thus in one embodiment, the method according to the invention comprises the steps of mutagenizing plant seeds (e.g. EMS mutagenesis), pooling of plant individuals or DNA, PCR amplification of a region of interest, heteroduplex formation and high-throughput detection, identification of the mutant plant, sequencing of the mutant PCR product. It is understood that other mutagenesis and selection methods may equally be used to generate such mutant plants.

[196] Instead of inducing mutations in PGAZ alleles, natural (spontaneous) mutant alleles may be identified by methods known in the art. For example, ECOTILLING may be used (Henikoff et al. 2004, Plant Physiology 135(2):630-6) to screen a plurality of plants or plant parts for the presence of natural mutant pgaz alleles. As for the mutagenesis techniques above, preferably Brassica species are screened which comprise an A and/or a C genome, so that the identified pgaz allele can subsequently be introduced into other Brassica species, such as Brassica napus, by crossing (inter- or intraspecific crosses) and selection. In ECOTILLING natural polymorphisms in breeding lines or related species are screened for by the TILLING methodology described above, in which individual or pools of plants are used for PCR amplification of the pgaz target, heteroduplex formation and high-throughput analysis. This can be followed by selecting individual plants having a required mutation that can be used subsequently in a breeding program to incorporate the desired mutant allele. [1 7] The identified mutant alleles can then be sequenced and the sequence can be compared to the wild type allele to identify the mutation(s). Optionally functionality can be tested as indicated above. Using this approach a plurality of mutant pgaz alleles (and Brassica plants comprising one or more of these) can be identified. The desired mutant alleles can then be combined with the desired wild type alleles by crossing and selection methods as described further below. Finally a single plant comprising the desired number of mutant pgaz and the desired number of wild type PGAZ alleles is generated.

[198] Oligonucleotides suitable as PCR primers or specific probes for detection of a specific mutant PGAZ allele can also be used to develop methods to determine the zygosity status of the specific mutant PGAZ allele.

[199] To determine the zygosity status of a specific mutant PGAZ allele, a PCR-based assay can be developed to determine the presence of a mutant and/or corresponding wild type PGAZ specific allele:

[200] To determine the zygosity status of a specific mutant PGAZ allele, two primers specifically recognizing the wild-type PGAZ allele can be designed in such a way that they are directed towards each other and have the mutation region located in between the primers. These primers may be primers specifically recognizing the 5' and 3' flanking sequences, respectively. This set of primers allows simultaneous diagnostic PCR amplification of the mutant, as well as of the corresponding wild type PGAZ allele.

[201] Alternatively, to determine the zygosity status of a specific mutant PGAZ allele, two primers specifically recognizing the wild-type PGAZ allele can be designed in such a way that they are directed towards each other and that one of them specifically recognizes the mutation region. These primers may be primers specifically recognizing the sequence of the 5' or 3' flanking region and the mutation region of the wild type PGAZ allele, respectively. This set of primers, together with a third primer which specifically recognizes the sequence of the mutation region in the mutant PGAZ allele, allow simultaneous diagnostic PCR amplification of the mutant PGAZ gene, as well as of the wild type PGAZ gene.

[202] Alternatively, to determine the zygosity status of a specific mutant PGAZ allele, two primers specifically recognizing the wild-type PGAZ allele can be designed in such a way that they are directed towards each other and that one of them specifically recognizes the joining region between the 5' or 3' flanking region and the mutation region. These primers may be primers specifically recognizing the 5' or 3' flanking sequence and the joining region between the mutation region and the 3' or 5' flanking region of the wild type PGAZ allele, respectively. This set of primers, together with a third primer which specifically recognizes the joining region between the mutation region and the 3' or 5' flanking region of the mutant PGAZ allele, respectively, allow simultaneous diagnostic PCR amplification of the mutant PGAZ gene, as well as of the wild type PGAZ gene. [203] Alternatively, the zygosity status of a specific mutant PGAZ allele can be determined by using alternative primer sets that specifically recognize mutant and wild type PGAZ alleles.

[204] A suitable method for determining the zygosity status of a mutant PGAZ allele comprises subjecting the genomic DNA of said plant, or a cell, part, seed or progeny thereof, to an amplification reaction using a set of at least two or at least three primers, wherein at least two of said primers specifically recognize the wild type PGAZ allele, said at least two primers being selected from the group consisting of:

(a) a first primer which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a second primer which specifically recognizes the mutation region of the wild type PGAZ allele, and

(b) a first primer which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a second primer which specifically recognizes the joining region between the 3' or 5' flanking region and the mutation region of the wild type PGAZ allele, respectively, and

wherein at least two of said primers specifically recognize the mutant PGAZ allele, said at least two primers being selected from the group consisting of: - 5 -

(a) the first primer which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a third primer which specifically recognizes the mutation region of the mutant PGAZ allele, and

(b) the first primer which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a third primer which specifically recognizes the joining region between the 3' or 5' flanking region and the mutation region of the mutant PGAZ allele, respectively.

[205] If the plant is homozygous for the mutant PGAZ gene or the corresponding wild type PGAZ gene, the diagnostic PCR assays described above will give rise to a single PCR product typical, preferably typical in length, for either the mutant or wild type PGAZ allele. If the plant is heterozygous for the mutant PGAZ allele, two specific PCR products will appear, reflecting both the amplification of the mutant and the wild type PGAZ allele.

[206] Identification of the wild type and mutant PGAZ specific PCR products can occur e.g. by size estimation after gel or capillary electrophoresis (e.g. for mutant PGAZ alleles comprising a number of inserted or deleted nucleotides which results in a size difference between the fragments amplified from the wild type and the mutant PGAZ allele, such that said fragments can be visibly separated on a gel); by evaluating the presence or absence of the two different fragments after gel or capillary electrophoresis, whereby the diagnostic PCR amplification of the mutant PGAZ allele can, optionally, be performed separately from the diagnostic PCR amplification of the wild type PGAZ allele; by direct sequencing of the amplified fragments; or by fluorescence-based detection methods.

[207] Examples of primers suitable to determine the zygosity of specific mutant PGAZ alleles are described in the Examples.

[208] Alternatively, to determine the zygosity status of a specific mutant PGAZ allele, a hybridization- based assay can be developed to determine the presence of a mutant and/or corresponding wild type PGAZ specific allele:

[209] To determine the zygosity status of a specific mutant PGAZ allele, two specific probes recognizing the wild-type PGAZ allele can be designed in such a way that each probe specifically recognizes a sequence within the PGAZ wild type allele and that the mutation region is located in between the sequences recognized by the probes. These probes may be probes specifically recognizing the 5' and 3' flanking sequences, respectively. The use of one or, preferably, both of these probes allows simultaneous diagnostic hybridization of the mutant, as well as of the corresponding wild type PGAZ allele.

[210] Alternatively, to determine the zygosity status of a specific mutant PGAZ allele, two specific probes recognizing the wild-type PGAZ allele can be designed in such a way that one of them ₅ specifically recognizes a sequence within the PGAZ wild type allele upstream or downstream of the mutation region, preferably upstream of the mutation region, and that one of them specifically recognizes the mutation region. These probes may be probes specifically recognizing the sequence of the 5' or 3' flanking region, preferably the 5' flanking region, and the mutation region of the wild type PGAZ allele, respectively. The use of one or, preferably, both of these probes, optionally, together with a third probe which specifically recognizes the sequence of the mutation region in the mutant PGAZ allele, allow diagnostic hybridization of the mutant and of the wild type PGAZ gene.

[211] Alternatively, to determine the zygosity status of a specific mutant PGAZ allele, a specific probe recognizing the wild-type PGAZ allele can be designed in such a way that the probe specifically recognizes the joining region between the 5' or 3' flanking region, preferably the 5' flanking region, and the mutation region of the wild type PGAZ allele. This probe, optionally, together with a second probe that specifically recognizes the joining region between the 5' or 3' flanking region, preferably the 5' flanking region, and the mutation region of the mutant PGAZ allele, allows diagnostic hybridization of the mutant and of the wild type PGAZ gene.

[212] Alternatively, the zygosity status of a specific mutant PGAZ allele can be determined by using alternative sets of probes that specifically recognize mutant and wild type PGAZ alleles.

[213] A suitable method for determining the zygosity status of a mutant PGAZ allele comprises subjecting the genomic DNA of said plant, or a cell, part, seed or progeny thereof, to a hybridization assay using a set of at least two specific probes, wherein at least one of said specific probes specifically recognizes the wild type PGAZ allele, said at least one probe selected from the group consisting of:

(a) a first probe which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a second probe which specifically recognizes the mutation region of the wild type PGAZ allele,

(b) a first probe which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a second probe which specifically recognizes the joining region between the 3' or 5' flanking region and the mutation region of the wild type PGAZ allele, respectively, and

(c) a probe which specifically recognizes the joining region between the 5' or 3' flanking region and the mutation region of the wild type PGAZ allele, and

wherein at least one of said specific probes specifically recognize(s) the mutant PGAZ allele, said at least one probe selected from the group consisting of:

(a) the first probe which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a third probe which specifically recognizes the mutation region of the mutant PGAZ allele, - 5 -

(b) the first probe which specifically recognizes the 5' or 3' flanking region of the mutant and the wild type PGAZ allele, and a third probe which specifically recognizes the joining region between the 5' or 3' flanking region and the mutation region of the mutant PGAZ allele, and

(c) a probe which specifically recognizes the joining region between the 5' or 3' flanking region and the mutation region of the mutant PGAZ allele.

[214] If the plant is homozygous for the mutant PGAZ gene or the corresponding wild type PGAZ gene, the diagnostic hybridization assays described above will give rise to a single specific hybridization product, such as one or more hybridizing DNA (restriction) fragments, typical, preferably typical in length, for either the mutant or wild type PGAZ allele. If the plant is heterozygous for the mutant PGAZ allele, two specific hybridization products will appear, reflecting both the hybridization of the mutant and the wild type PGAZ allele.

[215] Identification of the wild type and mutant PGAZ specific hybridization products can occur e.g. by size estimation after gel or capillary electrophoresis (e.g. for mutant PGAZ alleles comprising a number of inserted or deleted nucleotides which results in a size difference between the hybridizing DNA (restriction) fragments from the wild type and the mutant PGAZ allele, such that said fragments can be visibly separated on a gel); by evaluating the presence or absence of the two different specific hybridization products after gel or capillary electrophoresis, whereby the diagnostic hybridization of the mutant PGAZ allele can, optionally, be performed separately from the diagnostic hybridization of the wild type PGAZ allele; by direct sequencing of the hybridizing DNA (restriction) fragments; or by fluorescence-based detection methods.

[216] Examples of probes suitable to determine the zygosity of specific mutant PGAZ alleles are described in the Examples.

[217] Furthermore, detection methods specific for a specific mutant PGAZ allele that differ from PCR- or hybridization-based amplification methods can also be developed using the specific mutant PGAZ allele specific sequence information provided herein. Such alternative detection methods include linear signal amplification detection methods based on invasive cleavage of particular nucleic acid structures, also known as Invader™ technology, (as described e.g. in US patent 5,985,557 "Invasive Cleavage of Nucleic Acids", 6,001,567 "Detection of Nucleic Acid sequences by Invader Directed Cleavage, or Lyamichev et al., 1999, Nature Biotechnology 17: 292, incorporated herein by reference), RT-PCR- based detection methods, such as Taqman, or other detection methods, such as SNPlex. Briefly, in the Invader™ technology, the target mutation sequence may e.g. be hybridized with a labeled first nucleic acid oligonucleotide comprising the nucleotide sequence of the mutation sequence or a sequence spanning the joining region between the 3' flanking region and the mutation region, and with a second nucleic acid oligonucleotide comprising the 5' flanking sequence immediately downstream and adjacent to the mutation sequence, wherein the first and second oligonucleotide overlap by at least one ₅ nucleotide. Further, the target mutation sequence may e.g. be hybridized with a labeled first nucleic acid oligonucleotide complementary to the nucleotide sequence of the mutation sequence or a sequence spanning the joining region between the 5' flanking region and the mutation region, and with a second nucleic acid oligonucleotide complementary to the 3' flanking sequence immediately downstream and adjacent to the mutation sequence, wherein the first and second oligonucleotide overlap by at least one nucleotide.The duplex or triplex structure that is produced by this hybridization allows selective probe cleavage with an enzyme (Cleavase®) leaving the target sequence intact. The cleaved labeled probe is subsequently detected, potentially via an intermediate step resulting in further signal amplification. In a further embodiment, the first nucleic acid oligonucleotide comprises at its 5' end a 5' flap which is not complementary or corresponding to target mutant or wild type sequences, and immediately downstream of the flap the joining region between the 3' flanking region and the mutation region, wherein the mutation sequence is at the 5' end of said joining region, and said second nucleic acid oligonucleotide comprises the 5' flanking sequence immediately upstream of and contiguous with the mutation region, and at its 3' end immediately downstream of the 5' flanking sequence one additional nucleotide which may be any nucleotide. In another embodiment, the first nucleic acid oligonucleotide comprises at its 5' end a 5' flap which is not complementary or corresponding to target mutant or wild type sequences, and immediately downstream of the flap the sequence complementary to the joining region between the 5' flanking region and the mutation region, wherein complementary of the mutation sequence is at the 5' end of said joining region, and said second nucleic acid oligonucleotide complementary to the 3' flanking sequence immediately upstream of and contiguous with the mutation region, and at its 3' end immediately downstream of the complement to the 3 ' flanking sequence one additional nucleotide which may be any nucleotide. The length of the sequence corresponding to, or complementary to, the joining region in the first oligonucleotide may be at least 5, or at least 8, or at least 10, or at least 15, or at least 20, or at least 25, or at least 30, or at least 40, or at least 50 nucleotides. The length of the sequence corresponding to, or complementary to the flanking sequence in the second oligonucleotide may be at least 5, or at least 8, or at least 10, or at least 15, or at least 20, or at least 25, or at least 30, or at least 40, or at least 50 nucleotides. The length of the 5' flap of the first oligonucleotide may be at least 3, or at least 5, or at least 8, or at least 10, or at least 15, or at least 20 nucleotides.

[218] A suitable method for identifying a mutant PGAZ allele is a method comprising subjecting the biological sample to a hybridization assay with

(a) a labelled first nucleic acid oligonucleotide, said first nucleic acid oligonucleotide comprising the nucleotide sequence of the mutation sequence or a sequence spanning the joining region between the 3' flanking region and the mutation region, and a second nucleic acid oligonucleotide comprising the 5' flanking sequence immediately downstream and adjacent to the mutation sequence, and wherein the first and second oligonucleotide overlap by at least one nucleotide; or ₅

(b) a labelled first nucleic acid oligonucleotide, said first nucleic acid oligonucleotide

complementary to the nucleotide sequence of the mutation sequence or a sequence spanning the joining region between the 5' flanking region and the mutation region, and a second nucleic acid oligonucleotide complementary to the 3 ' flanking sequence immediately downstream and adjacent to the mutation sequence, and wherein the first and second oligonucleotide overlap by at least one nucleotide.

[219] Mutant PGAZ alleles can also be identified by determining the sequence of the PGAZ alleles. Sequencing can be performed by methods known in the art.

[220] A "kit", as used herein, refers to a set of reagents for the purpose of performing the method of the invention, more particularly, the identification of a specific mutant PGAZ allele in biological samples or the determination of the zygosity status of plant material comprising a specific mutant PGAZ allele. More particularly, a preferred embodiment of the kit of the invention comprises at least two specific primers, as described above, for identification of a specific mutant PGAZ allele, or at least two or three specific primers for the determination of the zygosity status. Optionally, the kit can further comprise any other reagent described herein in the PCR identification protocol. Alternatively, according to another embodiment of this invention, the kit can comprise at least one specific probe, which specifically hybridizes with nucleic acid of biological samples to identify the presence of a specific mutant PGAZ allele therein, as described above, for identification of a specific mutant PGAZ allele, or at least two or three specific probes for the determination of the zygosity status. Optionally, the kit can further comprise any other reagent (such as but not limited to hybridizing buffer, amplification buffer, label) for identification of a specific mutant PGAZ allele in biological samples, using the specific probe.

[221] The kit of the invention can be used, and its components can be specifically adjusted, for purposes of quality control (e.g., purity of seed lots), detection of the presence or absence of a specific mutant PGAZ allele in plant material or material comprising or derived from plant material, such as but not limited to food or feed products.

[222] The term "primer" as used herein encompasses any nucleic acid that is capable of priming the synthesis of a nascent nucleic acid in a template-dependent process, such as PCR. Typically, primers are oligonucleotides from 10 to 30 nucleotides, but longer sequences can be employed. Primers may be provided in double-stranded form, though the single-stranded form is preferred. Probes can be used as primers, but are designed to bind to the target DNA or RNA and need not be used in an amplification process.

[223] The term "recognizing" as used herein when referring to specific primers, refers to the fact that the specific primers specifically hybridize to a nucleic acid sequence in a specific mutant PGAZ allele under the conditions set forth in the method (such as the conditions of the PCR identification protocol), whereby the specificity is determined by the presence of positive and negative controls.

[224] The term "hybridizing", as used herein when referring to specific probes, refers to the fact that the probe binds to a specific region in the nucleic acid sequence of a specific mutant PGAZ allele under standard stringency conditions. Standard stringency conditions as used herein refers to the conditions for hybridization described herein or to the conventional hybridizing conditions as described by Sambrook et al., 1989 (Molecular Cloning: A Laboratory Manual, Second Edition, Cold Spring Harbour

Laboratory Press, NY) which for instance can comprise the following steps: 1) immobilizing plant genomic DNA fragments or BAC library DNA on a filter, 2) prehybridizing the filter for 1 to 2 hours at 65°C in 6 X SSC, 5 X Denhardt's reagent, 0.5% SDS and 20 μ^πιΐ denaturated carrier DNA, 3) adding the hybridization probe which has been labeled, 4) incubating for 16 to 24 hours, 5) washing the filter once for 30 min. at 68°C in 6X SSC, 0.1 %>SDS, 6) washing the filter three times (two times for 30 min. in 30ml and once for 10 min in 500ml) at 68°C in 2 X SSC, 0.1 %SDS, and 7) exposing the filter for 4 to 48 hours to X-ray film at -70°C.

[225] As used in herein, a "biological sample" is a sample of a plant, plant material or product comprising plant material. The term "plant" is intended to encompass plant tissues, at any stage of maturity, as well as any cells, tissues, or organs taken from or derived from any such plant, including without limitation, any seeds, leaves, stems, flowers, roots, single cells, gametes, cell cultures, tissue cultures or protoplasts. "Plant material", as used herein refers to material that is obtained or derived from a plant. Products comprising plant material relate to food, feed or other products that are produced using plant material or can be contaminated by plant material. It is understood that, in the context of the present invention, such biological samples are tested for the presence of nucleic acids specific for a specific mutant PGAZ allele, implying the presence of nucleic acids in the samples. Thus the methods referred to herein for identifying a specific mutant PGAZ allele in biological samples, relate to the identification in biological samples of nucleic acids that comprise the specific mutant PGAZ allele.

[226] The present invention also relates to the combination of specific PGAZ alleles in one plant, to the transfer of one or more specific mutant PGAZ allele(s) from one plant to another plant, to the plants comprising one or more specific mutant PGAZ allele(s), the progeny obtained from these plants and to plant cells, plant parts, and plant seeds derived from these plants.

[227] Thus, in one embodiment of the invention a method for combining two or more selected mutant PGAZ alleles in one plant is provided comprising the steps of:

(a) generating and/or identifying two or more plants each comprising one or more selected mutant PGAZ alleles, as described above,

(b) crossing a first plant comprising one or more selected mutant PGAZ alleles with a second plant comprising one or more other selected mutant PGAZ alleles, collecting Fl seeds from the cross, and, optionally, identifying an Fl plant comprising one or more selected mutant PGAZ alleles from the first plant with one or more selected mutant PGAZ alleles from the second plant, as described above,

(c) optionally, repeating step (b) until an Fl plant comprising all selected mutant PGAZ alleles is obtained,

(d) optionally,

identifying an Fl plant, which is homozygous or heterozygous for a selected mutant PGAZ allele by determining the zygosity status of the mutant PGAZ alleles, as described above, or generating plants which are homozygous for one or more of the selected mutant PGAZ alleles by performing one of the following steps:

extracting doubled haploid plants from treated microspore or pollen cells of Fl plants comprising the one or more selected mutant PGAZ alleles, as described above, selling the Fl plants comprising the one or more selected mutant PGAZ allele(s) for one or more generations (y), collecting Fl Sy seeds from the sellings, and identifying Fl Sy plants, which are homozygous for the one or more mutant PGAZ allele, as described above.

[228] In another embodiment of the invention a method for transferring one or more mutant PGAZ alleles from one plant to another plant is provided comprising the steps of:

(a) generating and/or identifying a first plant comprising one or more selected mutant PGAZ alleles, as described above, or generating the first plant by combining the one or more selected mutant PGAZ alleles in one plant, as described above (wherein the first plant is homozygous or heterozygous for the one or more mutant PGAZ alleles),

(b) crossing the first plant comprising the one or more mutant PGAZ alleles with a second plant not comprising the one or more mutant PGAZ alleles, collecting Fl seeds from the cross (wherein the seeds are heterozygous for a mutant PGAZ allele if the first plant was homozygous for that mutant PGAZ allele, and wherein half of the seeds are heterozygous and half of the seeds are azygous for, i.e. do not comprise, a mutant PGAZ allele if the first plant was heterozygous for that mutant PGAZ allele), and, optionally, identifying Fl plants comprising one or more selected mutant PGAZ alleles, as described above,

(c) backcrossing Fl plants comprising one or more selected mutant PGAZ alleles with the second plant not comprising the one or more selected mutant PGAZ alleles for one or more generations (x), collecting BCx seeds from the crosses, and identifying in every generation BCx plants comprising the one or more selected mutant I PGAZND alleles, as described above,

(d) optionally, generating BCx plants which are homozygous for the one or more selected mutant PGAZ alleles by performing one of the following steps:

extracting doubled haploid plants from treated microspore or pollen cells of BCx plants comprising the one or more desired mutant PGAZ allele(s), as described above,

selling the BCx plants comprising the one or more desired mutant PGAZ allele(s) for one or more generations (y), collecting BCx Sy seeds from the sellings, and identifying BCx Sy _5? plants, which are homozygous for the one or more desired mutant PGAZ allele, as described above.

[229] Said method for transferring one or more mutant PGAZ alleles from one plant to another is also suitable for combining one or more mutant PGAZ alleles in one plant, said method for combining at least two selected mutant PGAZ alleles comprising the steps of:

(a) identifying at least two plants each comprising at least one selected mutant PGAZ allele,

(b) crossing the at least two plants and collecting Fl hybrid seeds from the at least one cross, and

(c) optionally, identifying an Fl plant comprising at least two selected mutant PGAZ alleles.

[230] Said plants comprising said at least one selected mutant PGAZ alleles can be identified using the methods as described herein.

[231 ] In one aspect of the invention, the first and the second plant are Brassicaceae plants, particularly Brassica plants, especially Brassica napus plants or plants from another Brassica crop species. In another aspect of the invention, the first plant is a Brassicaceae plant, particularly a Brassica plant, especially a Brassica napus plant or a plant from another Brassica crop species, and the second plant is a plant from a Brassicaceae breeding line, particularly from a Brassica breeding line, especially from a Brassica napus breeding line or from a breeding line from another Brassica crop species. "Breeding line", as used herein, is a preferably homozygous plant line distinguishable from other plant lines by a preferred genotype and/or phenotype that is used to produce hybrid offspring.

[232] In yet another embodiment of the invention, a method for making a plant, in particular a Brassica crop plant, such as a Brassica napus plant, of which the pod drop resistance is increased is provided comprising combining and/or transferring mutant PGAZ alleles according to the invention in or to one Brassica plant, as described above.

[233] Also provided herein is a method to increase pod drop resistance, comprising introducing at least one mutant PGAZ allele into a Brassica plant, or comprising introducing the chimeric gene according to the invention in a Brassica plant.

[234] The mutant PGAZ allele can be introduced into said Brassica plants using methods as described herein comprising combining and/or transferring mutant PGAZ alleles according to the invention in or to one Brassica plant. The mutant PGAZ allele can also be introduced through, e.g. mutagenesis or gene targeting. Said method can further comprise indentification of the presence of the mutant PGAZ alleles using methods as described herein.

[235] The chimeric gene according to the invention can be introduced into Brassica plants using transformation. - 5 -

[236] A method to increase pod drop resistance may comprise

(a) providing plant cells with one or more chimeric genes to create transgenic plant cells, said chimeric genes comprising the following operably linked DNA fragments

i. a plant-expressible promoter;

ii. a DNA region, which when transcribed yields an RNA or protein molecule inhibitory to one or more PGAZ genes; and, optionally,

iii. a 3 ' end region involved in transcription termination and polyadenylation; regenerating a population of transgenic plant lines from said transgenic plant cell; and identifying a plant line with increased pod drop resistance within said population of transgenic plant lines.

[237] Means for preparing chimeric genes are well known in the art. Methods for making chimeric genes and vectors comprising such chimeric genes particularly suited to plant transformation are described in US4971908, US4940835, US4769061 and US4757011. The chimeric gene may also contain one or more additional nucleic acid sequences. [238] Said chimeric gene may be introduced in said Brassica plant by transformation. The term

"transformation" herein refers to the introduction (or transfer) of nucleic acid into a recipient host such as a plant or any plant parts or tissues including plant cells, protoplasts, calli, roots, tubers, seeds, stems, leaves, seedlings, embryos and pollen. Plants containing the transformed nucleic acid sequence are referred to as "transgenic plants". Transformed, transgenic and recombinant refer to a host organism such as a plant into which a heterologous nucleic acid molecule (e.g. an expression cassette or a recombinant vector) has been introduced. The nucleic acid can be stably integrated into the genome of the plant.

[239] As used herein, the phrase "transgenic plant" refers to a plant having an introduced nucleic acid stably introduced into a genome of the plant, for example, the nuclear or plastid genomes. In other words, plants containing transformed nucleic acid sequence are referred to as "transgenic plants".

Transgenic and recombinant refer to a host organism such as a plant into which a heterologous nucleic acid molecule (e.g. the promoter, the chimeric gene or the vector as described herein) has been introduced. The nucleic acid can be stably integrated into the genome of the plant.

[240] Transformation methods are well known in the art and include Agrobacterium-rnQdiatsd transformation. Agrobacterium-mediated transformation of cotton has been described e.g. in US patent 5,004,863, in US patent 6,483,013 and WO2000/71733. Plants may also be transformed by particle bombardment: Particles of gold or tungsten are coated with DNA and then shot into young plant cells or plant embryos. This method also allows transformation of plant plastids. Viral transformation

(transduction) may be used for transient or stable expression of a gene, depending on the nature of the virus genome. The desired genetic material is packaged into a suitable plant virus and the modified virus ₅ is allowed to infect the plant. The progeny of the infected plants is virus free and also free of the inserted gene. Suitable methods for viral transformation are described or further detailed e. g. in WO 90/12107, WO 03/052108 or WO 2005/098004. Further suitable methods well-known in the art are microinjection, electroporation of intact cells, polyethyleneglycol-mediated protoplast transformation, electroporation of protoplasts, liposome-mediated transformation, silicon-whiskers mediated transformation etc. Said transgene may be stably integrated into the genome of said plant cell, resulting in a transformed plant cell. The transformed plant cells obtained in this way may then be regenerated into mature fertile transformed plants.

[241] In one aspect of the invention, the plant according to the invention is a Brassica plant comprising at least two PGAZ genes wherein pod drop resistance is increased by combining and/or transferring three mutant PGAZ alleles according to the invention in or to the Brassica plant, as described above.

[242] In still another embodiment of the invention, a method for making a hybrid Brassica crop seed or plant comprising at least two PGAZ genes, in particular a hybrid Brassica napus seed or plant, of which the pod drop resistance is increased is provided, comprising the steps of:

(a) generating and/or identifying a first plant comprising a first and a second selected mutant PGAZ allele in homozygous state and a second plant comprising a third selected mutant PGAZ allele in homozygous state, as described above,

(b) crossing the first and the second plant and collecting Fl hybrid seeds from the cross. [243] In one aspect of the invention, the first or the second selected mutant PGAZ allele is the same mutant PGAZ allele as the third selected mutant PGAZ allele, such that the Fl hybrid seeds are homozygous for one mutant PGAZ allele and heterozygous for the other. In another aspect of the invention, the first plant is used as a male parent plant and the second plant is used as a female parent plant. [244] Whenever reference to a "plant" or "plants" according to the invention is made, it is understood that also plant parts (cells, tissues or organs, seed pods, seeds, severed parts such as roots, leaves, flowers, pollen, etc.), progeny of the plants which retain the distinguishing characteristics of the parents (especially the fruit dehiscence properties), such as seed obtained by selfing or crossing, e.g. hybrid seed (obtained by crossing two inbred parental lines), hybrid plants and plant parts derived there from are encompassed herein, unless otherwise indicated.

[245] In some embodiments, the plant cells of the invention, i.e. a plant cell comprising at least one mutant PGAZ allele, or a plant cell wherein expression of at least one PGAZ gene is reduced, as well as plant cells generated according to the methods of the invention, may be non-propagating cells. [246] The obtained plants according to the invention can be used in a conventional breeding scheme to produce more plants with the same characteristics or to introduce the characteristic of the presence of at least one mutant PGAZ allele, having reduced expression of at least one PGAZ in other varieties of the same or related plant species, or in hybrid plants. The obtained plants can further be used for creating propagating material. Plants according to the invention can further be used to produce gametes, seeds (including crushed seeds and seed cakes), seed oil, embryos, either zygotic or somatic, progeny or hybrids of plants obtained by methods of the invention. Seeds obtained from the plants according to the invention are also encompassed by the invention.

[247] "Creating propagating material", as used herein, relates to any means know in the art to produce further plants, plant parts or seeds and includes inter alia vegetative reproduction methods (e.g. air or ground layering, division, (bud) grafting, micropropagation, stolons or runners, storage organs such as bulbs, corms, tubers and rhizomes, striking or cutting, twin-scaling), sexual reproduction (crossing with another plant) and asexual reproduction (e.g. apomixis, somatic hybridization).

[248] As used herein "comprising" is to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more features, integers, steps or components, or groups thereof. Thus, e.g., a nucleic acid or protein comprising a sequence of nucleotides or amino acids, may comprise more nucleotides or amino acids than the actually cited ones, i.e., be embedded in a larger nucleic acid or protein. A chimeric gene comprising a nucleic acid which is functionally or structurally defined, may comprise additional DNA regions etc.

[249] All patents, patent applications, and publications or public disclosures (including publications on internet) referred to or cited herein are incorporated by reference in their entirety.

[250] The sequence listing contained in the file named„BCS14-2005-WOl_ST25.txt", which is 259 kilobytes (size as measured in Microsoft Windows®), contains 64 sequences SEQ ID NO: 1 through SEQ ID NO: 64 is filed herewith by electronic submission and is incorporated by reference herein.

[251] In the description and examples, reference is made to the following sequences:

SEQUENCES

SEQ ID No.l Arabidopsis thaliana PGAZ genomic sequence At2g

SEQ ID No.2 Arabidopsis thaliana PGAZ cDNA sequence

SEQ ID No.3 Arabidopsis thaliana PGAZ protein sequence

SEQ ID No.4 Brassica napus PGAZ-A1 genomic sequence

SEQ ID No.5 Brassica napus PGAZ-A1 cDNA sequence

SEQ ID No.6 Brassica napus PGAZ-A1 protein sequence _{Λ Λ}

- 61 -

SEQ ID No.7: Brassica napus PGAZ-A2 genomic sequence

SEQ ID No.8: Brassica napus PGAZ-A2 cDNA sequence

SEQ ID No.9: Brassica napus PGAZ-A2 protein sequence

SEQ ID No.10: Brassica napus PGAZ-C1 genomic sequence SEQ ID No.11 : Brassica napus PGAZ-C 1 cDNA sequence

SEQ ID No.12: Brassica napus PGAZ-C 1 protein sequence

SEQ ID No.13 : Brassica napus PGAZ-C2 genomic sequence

SEQ ID No.14: Brassica napus PGAZ-C2 cDNA sequence

SEQ ID No.15 : Brassica napus PGAZ-C2 protein sequence SEQ ID No.16: Brassica napus (line 2) PGAZ-Al genomic sequence

SEQ ID No.17: Brassica napus (line 2) PGAZ-Al cDNA sequence

SEQ ID No 18: Brassica napus (line 2) PGAZ-Al protein sequence

SEQ ID No.19: Brassica napus (line 2) PGAZ-A2 genomic sequence

SEQ ID No.20: Brassica napus (line 2) PGAZ-A2 cDNA sequence SEQ ID No.21 : Brassica napus (line 2) PGAZ-A2 protein sequence

SEQ ID No.22: Brassica napus (line 2) PGAZ-C 1 genomic sequence

SEQ ID No.23: Brassica napus (line 2) PGAZ-C 1 cDNA sequence

SEQ ID No.24: Brassica napus (line 2) PGAZ-C 1 protein sequence

SEQ ID No.25: Brassica napus (line 2) PGAZ-C2 genomic sequence SEQ ID No.26: Brassica napus (line 2) PGAZ-C2 cDNA sequence

SEQ ID No.27: Brassica napus (line 2) PGAZ-C2 protein sequence

SEQ ID No.28: Brassica rapa PGAZ-Al genomic sequence

SEQ ID No.29: Brassica rapa PGAZ-Al cDNA sequence

SEQ ID No.30: Brassica rapa PGAZ-Al protein sequence

SEQ ID No.31 : Brassica rapa PGAZ-A2 genomic sequence

SEQ ID No.32: Brassica rapa PGAZ-A2 cDNA sequence

SEQ ID No.33: Brassica rapa PGAZ-A2 protein sequence

SEQ ID No.34: Brassica oleracea PGAZ-C1 genomic sequence

SEQ ID No.35: Brassica oleracea PGAZ-C1 cDNA sequence SEQ ID No.36: Brassica oleracea PGAZ-C 1 protein sequence

SEQ ID No.37: Brassica oleracea PGAZ-C2 genomic sequence

SEQ ID No.38: Brassica oleracea PGAZ-C2 cDNA sequence

SEQ ID No.39: Brassica oleracea PGAZ-C2 protein sequence

SEQ ID No.40: Brassica nigra PGAZ-B 1 genomic sequence SEQ ID No.41 : Brassica nigra PGAZ-B1 cDNA sequence

SEQ ID No.42: Brassica nigra PGAZ-B1 protein sequence

SEQ ID No.43: Brassica nigra PGAZ-B2 genomic sequence

SEQ ID No.44: Brassica nigra PGAZ-B2 cDNA sequence -

SEQ ID No 45: Brassica nigra PGAZ-B2 protein sequence

SEQ ID No 46: Primer A1-EMS05-FAM

SEQ ID No 47: Primer A1-EMS05-VIC

SEQ ID No 48: Primer Al-EMS05-common

SEQ ID No 49: Primer A1-EMS03 1

SEQ ID No 50: Primer A1-EMS03 2

SEQ ID No 51 : Probe A1-EMS03-FAM

SEQ ID No 52: Probe A1-EMS03-VIC

SEQ ID No 53: Primer A2-EMS06-FAM

SEQ ID No 54: Primer A2-EMS06-VIC

SEQ ID No 55: Primer A2-EMS06-common

SEQ ID No 56: Primer A2-EMS 11 -FAM

SEQ ID No 57: Primer A2-EMS 11 -VIC

SEQ ID No 58: Primer A2-EMS 11 -common

SEQ ID No 59: Primer C 1 -EMS01 -FAM

SEQ ID No 60: Primer Cl-EMSOl -VIC

SEQ ID No 61 : Primer C1-EMS01 -common

SEQ ID No 62: Primer C2-EMS 13 -FAM

SEQ ID No 63: Primer C2-EMS13-VIC

SEQ ID No 64: Primer C2-EMS 13 -common

EXAMPLES

[252] Unless stated otherwise in the Examples, all recombinant DNA techniques are carried out according to standard protocols as described in Sambrook and Russell (2001) Molecular Cloning: A Laboratory Manual, Third Edition, Cold Spring Harbor Laboratory Press, NY, in Volumes 1 and 2 of Ausubel et al. (1994) Current Protocols in Molecular Biology, Current Protocols, USA and in Volumes I and II of Brown (1998) Molecular Biology LabFax, Second Edition, Academic Press (UK). Standard materials and methods for plant molecular work are described in Plant Molecular Biology Labfax (1993) by R.D.D. Croy, jointly published by BIOS Scientific Publications Ltd (UK) and Blackwell Scientific Publications, UK. Standard materials and methods for polymerase chain reactions can be found in Dieffenbach and Dveksler (1995) PCR Primer: A Laboratory Manual, Cold Spring Harbor Laboratory

Press, and in McPherson at al. (2000) PCR - Basics: From Background to Bench, First Edition, Springer Verlag, Germany. Example 1 - Isolation of the DNA sequences of the PGAZ genes

[253] The PGAZ sequences from two Brassica napus lines, from Brassica rapa, Brassica oleracea and Brassica nigra have been determined as follows.

[254] Genomic DNA from Brassica napus was isolated using standard procedures. Fragments of the PGAZ gene were isolated through PCR on the B. napus genomic DNA using primers based on the B. napus PGAZ sequence as described by Gonzalez-Carranza et al., 2002, Plant Physiol 128:534. The PCR products were cloned and the sequence was determined.

[255] Subsequently, PGAZ sequences from the PCR products were used as the query in a BLAST homology search of in-house sequence databases of two Brassica napus lines, Brassica rapa, Brassica nigra, and Brassica oleracea. Four PGAZ genes were identified in each of the B. napus lines, and two PGAZ genes in B. rapa, B. nigra and B. oleracea. The genes and coding regions of the PGAZ sequences were determined using EST sequence information and comparison with the Arabidopsis PGAZ gene At2g41850 sequence information. The Brassica PGAZ sequences have nine exons.

[256] SEQ ID NOs: 4, 7, 10 and 13 are the genomic sequences of BnPGAZ-Al, BnPGAZ-A2, BnPGAZ-Cl and BnPGAZ-C2, respectively of the first B. napus line. SEQ ID NOs: 5, 8, 11 and 14 are the cDNA sequences of BnPGAZ-Al, BnPGAZ-A2, BnPGAZ-Cl and BnPGAZ-C2, respectively.

Proteins encoded by BnPGAZ-Al, BnPGAZ-A2, BnPGAZ-Cl and BnPGAZ-C2 are given in SEQ ID NOs: 6, 9, 12 and 15, respectively.

[257] SEQ ID NOs: 16, 19, 22 and 25 are the genomic sequences of BnPGAZ-Al, BnPGAZ-A2, BnPGAZ-Cl and BnPGAZ-C2, respectively of the second B. napus line. SEQ ID NOs: 17, 20, 23 and 26 are the cDNA sequences of BnPGAZ-Al, BnPGAZ-A2, BnPGAZ-Cl and BnPGAZ-C2, respectively. Proteins encoded by BnPGAZ-Al, BnPGAZ-A2, BnPGAZ-Cl and BnPGAZ-C2 are given in SEQ ID NOs: 18, 21, 24 and 27, respectively.

[258] 2 PGAZ gene homologs were identified for B. rapa (BrPGAZ-Al (SEQ ID No. 28) and BrPGAZ-A2 (SEQ ID NO: 31)), for B. oleracea (BoPGAZ-Cl (SEQ ID No. 34) and BoPGAZ-C2 (SEQ

ID No. 37)), and for B. nigra (BniPGAZ-B 1 (SEQ ID No: 40) and BniPGAZ-B2 (SEQ ID NO: 43)). cDNAs corresponding to these sequences were predicted using FgeneSH software, and are depicted in

SEQ ID No. 29, SEQ ID No. 32, SEQ ID No. 35, SEQ ID No. 38, SEQ ID NO: 41 and SEQ ID NO: 44 for BrPGAZ-Al, BrPGAZ-A2, BoPGAZ-Cl, BoPGAZ-C2, BniPGAZ-B 1 and BniPGAZ-B2, respectively. The proteins encoded by BrPGAZ-Al, BrPGAZ-A2, BoPGAZ-Cl, BoPGAZ-C2,

BniPGAZ-B 1 and BniPGAZ-B2 are depicted in SEQ ID No. 30, SEQ ID No. 33, SEQ ID No. 36, SEQ

ID No. 39, SEQ ID NO: 42 and SEQ ID NO: 45, respectively. Example 2 - Expression of Brassica PGAZ g

[259] Relative expression of the four BnPGAZ genes in different tissues was determined using in silico expression analysis based on BGI Solexa mRNA data of Brassica napus. The expression analysis showed that BnPGAZ-Cl is expressed in roots and in seed 49 days after flowering, and that BnPGAZ- C2 is expressed in flowers (Figure 1).

[260] Relative PGAZ expression analyzed in more detail in leaf pedicel (48 days after sowing DAS)) and pod pedicel (47 days after flowering (DAF)). Therefore, mRNA was isolated from the leaf pedicel and the pod pedicel tissues, and the relative abundance of mRNA of the different PGAZ genes was determined by RT-PCR amplification of the different PGAZ sequences. The obtained PCR products were cloned in a standard vector and, for each of the tissues, 100 clones were sequenced. The number of clones in the 100 sequenced clones for the different PGAZ genes is shown in Figure 2. The four PGAZ genes have a similar relative abundance in the leaf pedicel. In the pod pedicel, the abundance of BnPGAZ-Cl, and in particular BnPGAZ- A2, is higher than of BnPGAZ-Al and BnPGAZ-C2, indicating that BnPGAZ-Cl and BnPGAZ- A2 have the highest expression levels in the pod pedicel. Example 3 - Generation and isolation of mutant PGAZ alleles

[261] Mutations in the PGAZ genes of Brassica napus identified in Example 1 were generated and identified as follows:

- 30,000 seeds from an elite spring oilseed rape breeding line (M0 seeds) were pre-imbibed for 2 h on wet filter paper in deionized or distilled water. Half of the seeds were exposed to 0.8% EMS and half to 1% EMS (Sigma: M0880) and incubated for 4 h.

- The mutagenized seeds (Ml seeds) were rinsed three times and dried in a fume hood overnight.

30,000 Ml plants were grown in soil and selfed to generate M2 seeds. M2 seeds were harvested for each individual Ml plant.

- Two times 4800 M2 plants, derived from different Ml plants, were grown and DNA samples were prepared from leaf samples of each individual M2 plant according to the CTAB method (Doyle and

Doyle, 1987, Phytochemistry Bulletin 19:11-15).

- The DNA samples were screened for the presence of point mutations in the PGAZ genes that cause the introduction of STOP codons and another amino acid in the protein-encoding regions of the PGAZ genes, by direct sequencing by standard sequencing techniques (LGC) and analyzing the sequences for the presence of the point mutations using the NovoSNP software (VIB Antwerp).

- The mutant PGAZ alleles as depicted in Table 2 were thus identified. _r

[262] Table 2: STOP codon mutations in PGAZ

Seeds of plants comprising alleles PGAZ-A1 -EMS03 and PGAZ-C1-EMS01 in homozygous state have been deposited at the the NCIMB, Ferguson Building, Craibstone Estate, Bucksbum, Aberdeen, AB 21 9YA UK, under the Budapest Treaty on 3 July 2014, under accession number NCIMB 42263; seeds of plants comprising alleles PGAZ-A1-EMS05 and PGAZ-C1-EMS01 in homozygous state have been deposited at the the NCIMB, Ferguson Building, Craibstone Estate, Bucksbum, Aberdeen, AB 21 9YA UK, under the Budapest Treaty on 3 July 2014, under accession number NCIMB 42264; seeds of plants comprising alleles PGAZ-A2-EMS06 and PGAZ-C2-EMS 13 in homozygous state have been deposited at the the NCIMB, Ferguson Building, Craibstone Estate, Bucksbum, Aberdeen, AB 21 9YA UK, under the Budapest Treaty on 3 July 2014, under accession number NCIMB 42265; and seeds of plants comprising alleles PGAZ-A2-EMS11 and PGAZ-C2-EMS13 in homozygous state have been deposited at the the NCIMB, Ferguson Building, Craibstone Estate, Bucksbum, Aberdeen, AB 21 9YA UK, under the Budapest Treaty on 3 July 2014, under accession number NCIMB 42266. Example 4 - Identification of a Brassica plant comprising a mutant Brassica PGAZ allele

[263] Brassica plants comprising the mutations in the PGAZ genes identified in Example 4 were identified as follows:

For each mutant PGAZ gene identified in the DNA sample of an M2 plant, at least 50 M2 plants derived from the same Ml plant as the M2 plant comprising the PGAZ mutation, were grown and

DNA samples were prepared from leaf samples of each individual M2 plant.

The DNA samples were screened for the presence of the identified point PGAZ mutation as described above in Example 4.

Heterozygous and homozygous (as determined based on the electropherograms) M2 plants comprising the same mutation were selfed and M3 seeds were harvested.

Example 5 - Analysis of the pod drop resistance of Brassica plants comprising mutant PGAZ alleles

[264] Brassica plants homozygous for different PGAZ genes were grown in the greenhouse until complete maturity. The force required for detachment of the pods from the plants was measured with a force gauge (FGV-1XY Digital Force Gauge with USB). To this end, from each plant, ropes were attached to the pedicel of pods from the main branch (except for the first 10 pods from below the main branch). The force gauge was attached to the pods, and pulled slowly such that the rope makes an angle of 90° with the pod. The pod drop resistance was measured for 25 pods per plant, and 3 or 4 plants per genotype. The force (Fg) (in grams) were statistically analyzed using an ANOVA in which the values for different plants were treated as repetitions. The results of the analysis are shown in Tables 3 and 4, and Figures 3 and 4.

[265] Table 3: Force (Fg) in grams required for detachment of the pods from the plants in double mutant plants for different PGAZ genes grown in the greenhouse. - Represents wild-type alleles, whereas Al, A2, CI and C2 represent the mutant alleles.

A. F1S1 non BC generation

_n

- 67 -

PGAZ-A2-EMS11/PGAZ-Cl-EMSOl (A2A2/~) 72.87 4.41 8.64 PGAZ-A2-EMS11/PGAZ-Cl-EMSOl (A2A2/C1C1) 81.93 5.32 10.43

PGAZ- A2-EMS06/PGAZ-C 1 -EMSO 1 (-/-) 61.47 3.87 7.58 PGAZ- A2-EMS06/PGAZ-C 1 -EMSO 1 (-/C 1 C 1 ) 134.21 8.73 17.12 PGAZ- A2-EMS06/PGAZ-C 1 -EMSO 1 (A2A2/~) 99.49 6.13 12.02 PGAZ- A2-EMS06/PGAZ-C 1 -EMSO 1 (A2A2/C 1 C 1 ) 77.08 6.67 13.07

PGAZ- Al -EMS05/PGAZ-C 1 -EMSO 1 (-/-) 66.51 5.33 10.44 PGAZ- Al -EMS05/PGAZ-C 1 -EMSO 1 (~/C 1 C 1 ) 91.14 5.05 9.89 PGAZ- Al -EMS05/PGAZ-C 1 -EMSO 1 (A1A1/-) 137.52 7.22 14.16 PGAZ- Al -EMS05/PGAZ-C 1 -EMSO 1 (Al Al /C 1 C 1 ) 102.11 8.44 16.54

PGAZ- Al -EMS03/PGAZ-C 1 -EMSO 1 (-/-) 37.75 4.41 8.65 PGAZ- Al -EMS03/PGAZ-C 1 -EMSO 1 (~/C 1 C 1 ) 101.73 7.77 15.24 PGAZ- Al -EMS03/PGAZ-C 1 -EMSO 1 (A1A1/-) 99.61 9.18 17.99 PGAZ- Al -EMS03/PGAZ-C 1 -EMSO 1 (AlAl/ClCl) 38.51 3.25 6.37

B. BC1S1 generation

[266] Table 4: Force (Fg) in grams required for detachment of the pods from the plants in quadruple mutant plants for different PGAZ genes grown in the greenhouse. Plants were of the BC1 S1 generation.

- Represents wild-type alleles, whereas Al, A2, CI and C2 represent the mutant alleles.

Genotype Mean SE LSD CI. lower Cl.upper

PGAZ-A1 -EMS03/PG AZ- A2-EMS06/PGAZ-C 1 -EMS01 /PGAZ-C2-EMS 13

(-/-/-/-) 153.06 11.51 22.55 130.51 175.61

(~/~/~/C2C2) 163.01 11.51 22.55 140.46 185.56

(~/~/ClCl/~) 241.05 11.51 22.55 218.50 263.60

(~/A2A2/~/~) 246.80 11.51 22.55 224.25 269.35

(A1A1/-/-/-) 245.07 11.51 22.55 222.52 267.62

(-/-/C1C1/C2C2) 167.91 11.51 22.55 145.36 190.46

(-/A2A2/-/C2C2) 235.67 11.51 22.55 213.12 258.22

(-/A2A2/C1C1/-) 271.35 11.51 22.55 248.80 293.90

(A1A1/-/-/C2C2) 183.64 11.51 22.55 161.09 206.19

(A1A1/-/C1C1/-) 200.11 11.51 22.55 177.56 222.66

(A1A1/A2A2/-/-) 198.67 11.51 22.55 176.12 221.22

(-/A2A2/C1C1/C2C2) 179.93 11.51 22.55 157.38 202.48

(A1A1/-/C1C1/C2C2) 231.45 11.51 22.55 208.90 254.00

(A1A1/A2A2/-/C2C2) 174.17 11.51 22.55 151.62 196.72

(A1A1/A2A2/C1C1/-) 258.42 11.51 22.55 235.87 280.97

(A1A1/A2A2/C1C1/C2C2) 206.22 11.51 22.55 183.67 228.77

PGAZ-Al -EMS05/PG AZ- A2-EMS 11/PGAZ-C 1 -EMS01 /PGAZ-C2-EMS 13

(-/-/-/-) 75.71 8.78 17.20 58.50 92.91

(~/~/~/C2C2) 122.35 8.78 17.20 105.14 139.55

(~/~/ClCl/~) 96.61 8.78 17.20 79.41 113.82

(~/A2A2/~/~) 107.05 15.20 29.80 77.25 136.85

(A1A1/-/-/-) 120.18 8.78 17.20 102.98 137.38

(-/-/C1C1/C2C2) 172.28 10.75 21.07 151.21 193.35

(-/A2A2/-/C2C2) 137.46 8.78 17.20 120.26 154.66

(-/A2A2/C1C1/-) 160.21 8.78 17.20 143.00 177.41

(A1A1/-/-/C2C2) 95.98 8.78 17.20 78.78 113.19

(A1A1/-/C1C1/-) 171.91 8.78 17.20 154.71 189.12

(A1A1/A2A2/-/-) 137.36 8.78 17.20 120.16 154.57

(-/A2A2/C1C1/C2C2) 228.32 8.78 17.20 211.12 245.52

(A1A1/-/C1C1/C2C2) 176.89 8.78 17.20 159.68 194.09

(A1A1/A2A2/-/C2C2) 168.24 8.78 17.20 151.03 185.44

(A1A1/A2A2/C1C1/-) 205.64 8.78 17.20 188.44 222.85

(A1A1/A2A2/C1C1/C2C2) 238.05 8.78 17.20 220.84 255.25

Wild-type control 154.04 6.87 13.47 140.57 167.51 [267] It can be observed that all mutant PGAZ alleles contribute to an increase in force for detachment of the pods, i.e. to an increase in pod drop resistance. There is a trend towards an increasing pod drop resistance with increasing number of mutant PGAZ alleles.

Example 6 - Analysis of yield of Brassica plants comprising mutant PGAZ alleles [268] Brassica plants homozygous for different mutant PGAZ alleles are grown in the field and seed yield is determined. An increasing number of mutant PGAZ alleles increases the seed yield.

Example 7 - Detection and/or transfer of mutant PGAZ genes into (elite) Brassica lines

[269] To select for plants comprising a point mutation in a PGAZ allele, direct sequencing by standard sequencing techniques known in the art, such as those described in Example 4, can be used.

Alternatively, PCR assays can be developed to discriminate plants comprising a specific point mutation in a PGAZ allele from plants not comprising that specific point mutation. The following discriminating Taqman PCR assays were thus developed to detect the presence or absence and the zygosity status of the mutant alleles identified in Example 4 (see Table 2):

- Template DNA:

- Genomic DNA isolated from leaf material of homozygous or heterozygous mutant Brassica plants (comprising a mutant PGAZ allele, called hereinafter "PGAZ-Xx-EMSXX").

- Wild type DNA control: Genomic DNA isolated from leaf material of wild type Brassica plants (comprising the wild type equivalent of the mutant PGAZ allele, called hereinafter "WT").

- Positive DNA control: Genomic DNA isolated from leaf material of homozygous mutant Brassica plants known to comprise PGAZ-Xx-EMSXX.

- Primers and probes for the mutant and corresponding wild type target PGAZ gene are indicated in

Table 5.

[270] Table 5: Primers and probes for detection of wild type and mutant PGAZ alleles

Claims

CLAIMS:

1. A Brassica plant comprising at least two PGAZ genes, comprising at least one mutant PGAZ allele in its genome.

2. The plant according to claim 1, wherein said mutant PGAZ allele is a mutant allele of a PGAZ gene comprising a nucleic acid sequence selected from the group consisting of:

(a) a nucleotide sequence which comprises at least 90% sequence identity to SEQ ID NO: 1, SEQ ID NO: 4, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 13, SEQ ID NO: 16, SEQ ID NO: 19, SEQ ID NO: 22, SEQ ID NO: 25, SEQ ID NO: 28, SEQ ID NO: 31, SEQ ID NO: 34, SEQ ID NO: 37, SEQ ID NO: 40, or SEQ ID NO: 43;

(b) a nucleotide sequence comprising a coding sequence which comprises at least 90% sequence identity to SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 8, SEQ ID NO: 11, SEQ ID NO: 14, SEQ ID NO: 17, SEQ ID NO: 20, SEQ ID NO: 23, SEQ ID NO: 26, SEQ ID NO: 29, SEQ ID NO: 32, SEQ ID NO: 35, SEQ ID NO: 38, SEQ ID NO: 41, or SEQ ID NO: 44; and

(c) a nucleotide sequence encoding an amino acid sequence which comprises at least 90%> sequence identity to SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 12, SEQ ID NO: 15, SEQ ID NO: 18, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 27, SEQ ID NO: 30, SEQ ID NO: 33, SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, or SEQ ID NO 45.

3. The plant according to claim 1 or 2, which is a Brassica plant comprising four PGAZ genes, said Brassica plant selected from the group consisting of Brassica napus, Brassica juncea and Brassica carinata.

4. The plant according to any one of claims 1 to 3, comprising at least two mutant PGAZ alleles, or at least three mutant PGAZ alleles, or at least four mutant PGAZ alleles, or at least five mutant PGAZ alleles, or at least six mutant PGAZ alleles, or at least seven mutant PGAZ alleles, or at least eight mutant PGAZ alleles.

5. The plant according to any one of claims 1 to 4, wherein said mutant PGAZ allele is selected from the group consisting of:

(a) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 2422 of SEQ ID NO: 4;

(b) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 2140 of SEQ ID NO: 4;

(c) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 2212 of SEQ ID NO: 4; (d) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3356 of SEQ ID NO: 7;

(e) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 3531 of SEQ ID NO: 7;

(f) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 3245 of SEQ ID NO: 7;

(g) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 3275 of SEQ ID NO: 7;

(h) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 2361 of SEQ ID NO: 10;

(i) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 2442 of SEQ ID NO: 10;

(j) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 2464 of SEQ ID NO: 13;

(k) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 2473 of SEQ ID NO: 13.

6. The plant according to any one of claims 1 to 5, which is homozygous for the mutant PGAZ allele.

7. A Brassica plant comprising at least two PGAZ genes, wherein expression of at least one PGAZ gene is reduced.

8. The plant according to any one of claims 1 to 7, which has increased pod drop resistance.

9. A plant cell, pod, seed, or progeny of the plant of any one of claims 1 to 8.

10. A mutant allele of a Brassica PGAZ gene, wherein the PGAZ gene is selected from the group

consisting of:

(a) a nucleotide sequence which comprises at least 90% sequence identity to SEQ ID NO: 1, SEQ ID NO: 4, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 13, SEQ ID NO: 16, SEQ ID

NO: 19, SEQ ID NO: 22, SEQ ID NO: 25, SEQ ID NO: 28, SEQ ID NO: 31, SEQ ID NO: 34, SEQ ID NO: 37, SEQ ID NO: 40, or SEQ ID NO: 43;

(b) a nucleotide sequence comprising a coding sequence which comprises at least 90% sequence identity to SEQ ID NO: 2, SEQ ID NO: 5, SEQ ID NO: 8, SEQ ID NO: 11, SEQ ID NO: 14, SEQ ID NO: 17, SEQ ID NO: 20, SEQ ID NO: 23, SEQ ID NO: 26, SEQ ID NO: 29, SEQ

ID NO: 32, SEQ ID NO: 35, SEQ ID NO: 38, SEQ ID NO: 41, or SEQ ID NO: 44; and

11. The mutant allele according to claim 10, selected from the group consisting of:

position 2422 of SEQ ID NO: 4;

position 2140 of SEQ ID NO: 4;

position 2212 of SEQ ID NO: 4;

(d) a mutant PGAZ allele comprising a C to T substitution at a position corresponding to

position 3356 of SEQ ID NO: 7;

position 3531 of SEQ ID NO: 7;

position 3245 of SEQ ID NO: 7;

position 3275 of SEQ ID NO: 7;

position 2361 of SEQ ID NO: 10;

position 2442 of SEQ ID NO: 10;

position 2464 of SEQ ID NO: 13;

position 2473 of SEQ ID NO: 13.

12. A chimeric gene comprising the following operably linked DNA fragments:

(a) a plant-expressible promoter;

(b) a DNA region, which when transcribed yields an RNA or protein molecule inhibitory to one or more PGAZ genes; and, optionally,

(c) a 3 ' end region involved in transcription termination and polyadenylation.

13. A method for identifying a mutant PGAZ allele according to claim 10 or 11 in a biological sample, which comprises determining the presence of a mutant PGAZ specific region in a nucleic acid present in said biological sample.

14. A method for determining the zygosity status of a mutant PGAZ allele according to claim 10 or 11 in a Brassica plant, plant material or seed, which comprises determining the presence of a mutant and/or a corresponding wild type PGAZ specific region in the genomic DNA of said plant, plant material or seed.

15. A kit for identifying a mutant PGAZ allele according to claim 10 or 11, in a biological sample, comprising a set of at least two primers, said set being selected from the group consisting of:

(b) a set of primers, wherein one of said primers specifically recognizes the 5' or 3' flanking region of the mutant PGAZ allele and the other of said primers specifically recognizes the joining region between the 3' or 5' flanking region and the mutation region of the mutant PGAZ allele, respectively;

or said kit comprising a set of at least one probe, said probe being selected from the group consisting of:

(b) a probe specifically recognizing the joining region between the 3' or 5' flanking region

between the mutation region of the mutant PGAZ allele.

16. A method for transferring at least one selected mutant PGAZ allele according to claim 10 or 11, from one plant to another plant comprising the steps of:

(a) identifying a first plant comprising at least one selected mutant PGAZ allele using the method according to claim 13,

(b) crossing the first plant with a second plant not comprising the at least one selected mutant PGAZ allele and collecting Fl hybrid seeds from said cross,

(c) optionally, identifying Fl plants comprising the at least one selected mutant PGAZ allele using the method according to claim 13,

(d) backcrossing the Fl plants comprising the at least one selected mutant PGAZ allele with the second plant not comprising the at least one selected mutant PGAZ allele for at least one generation (x) and collecting BCx seeds from said crosses, and

(e) identifying in every generation BCx plants comprising the at least one selected mutant PGAZ allele using the method according to the method of claim 13.

17. A method to increase pod drop resistance, comprising

a. introducing at least one mutant PGAZ allele into a Brassica plant; or

b. introducing the chimeric gene of claim 12 into a Brassica plant.

18. A method for production of seeds, said method comprising sowing the seeds according to claim 9, growing plants from said seeds, and harvesting seeds from said plants.

19. A Brassica plant selected from the group consisting of:

(a) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2422 of SEQ ID NO: 4 and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2361 of SEQ ID NO: 10, reference seeds comprising said allele having been deposited at the NCIMB Limited on 3 July 2014, under accession number NCIMB 42263;

(b) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2212 of SEQ ID NO: 4, and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2361 of SEQ ID NO: 10, reference seeds comprising said allele having been deposited at the NCIMB Limited on ; July 2014, under accession number NCIMB 42264,

(c) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3356 of SEQ ID NO: 7 and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2473 of SEQ ID NO: 13, reference seeds comprising said allele having been deposited at the NCIMB Limited on 3 July 2014, under accession number NCIMB 42265; and

(d) a Brassica plant comprising a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 3275 of SEQ ID NO: 7 and a mutant PGAZ allele comprising a C to T substitution at a position corresponding to position 2473 of SEQ ID NO: 13, reference seeds comprising said alleles having been deposited at the NCIMB Limited on 3 July 2014, under accession number NCIMB 42266.

20. Use of the mutant PGAZ alleles according to claim 10 or 11 or the chimeric gene according to claim 12 to increase pod drop resistance.

21. Use of the plants according to any one of claims 1 to 8, or of the seeds according to claim 9, to produce oilseed rape oil or an oilseed rape seed cake.

22. A method for producing food, feed, or an industrial product comprising

a. obtaining the plant or a part thereof, of any one of claims 1 to 8 or the seeds of claim 9, and b. preparing the food, feed or industrial product from the plant or part thereof.

23. The method of claim 22, wherein

a. the food or feed is oil, meal, grain, starch, flour or protein; or

b. the industrial product is biofuel, industrial chemicals, a pharmaceutical or a nutraceutical.