WO2014152759A2 - Methods of creating fungi tolerant corn plants and compositions thereof - Google Patents

Methods of creating fungi tolerant corn plants and compositions thereof Download PDF

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Publication number
WO2014152759A2
WO2014152759A2 PCT/US2014/027702 US2014027702W WO2014152759A2 WO 2014152759 A2 WO2014152759 A2 WO 2014152759A2 US 2014027702 W US2014027702 W US 2014027702W WO 2014152759 A2 WO2014152759 A2 WO 2014152759A2
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Prior art keywords
marker
seq
tolerance
markers
plant
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PCT/US2014/027702
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French (fr)
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WO2014152759A3 (en
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Marcelo P. GIOVANINI
Yule PAN
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Monsanto Technology Llc
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    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01H—NEW PLANTS OR NON-TRANSGENIC PROCESSES FOR OBTAINING THEM; PLANT REPRODUCTION BY TISSUE CULTURE TECHNIQUES
    • A01H1/00—Processes for modifying genotypes ; Plants characterised by associated natural traits
    • A01H1/04—Processes of selection involving genotypic or phenotypic markers; Methods of using phenotypic markers for selection
    • A01H1/045—Processes of selection involving genotypic or phenotypic markers; Methods of using phenotypic markers for selection using molecular markers
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01H—NEW PLANTS OR NON-TRANSGENIC PROCESSES FOR OBTAINING THEM; PLANT REPRODUCTION BY TISSUE CULTURE TECHNIQUES
    • A01H5/00—Angiosperms, i.e. flowering plants, characterised by their plant parts; Angiosperms characterised otherwise than by their botanic taxonomy
    • A01H5/10—Seeds
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01H—NEW PLANTS OR NON-TRANSGENIC PROCESSES FOR OBTAINING THEM; PLANT REPRODUCTION BY TISSUE CULTURE TECHNIQUES
    • A01H6/00—Angiosperms, i.e. flowering plants, characterised by their botanic taxonomy
    • A01H6/46—Gramineae or Poaceae, e.g. ryegrass, rice, wheat or maize
    • A01H6/4684—Zea mays [maize]
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
    • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
    • C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
    • C12Q1/6876—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes
    • C12Q1/6888—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes for detection or identification of organisms
    • C12Q1/6895—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes for detection or identification of organisms for plants, fungi or algae
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
    • C12Q2600/00—Oligonucleotides characterized by their use
    • C12Q2600/13—Plant traits

Definitions

  • the present invention relates to the field of agricultural biotechnology. More specifically, the invention involves methods for producing corn plants containing one or more markers that are associated with tolerance to fungi.
  • the present invention provides a method of producing a corn plant with anthracnose stalk rot (ASR) tolerance comprising introgressing a chromosomal locus defined as flanked by markers TIDP7054 and AY104360, that is associated with ASR tolerance, wherein the locus is introgressed into a plant lacking the locus.
  • the introgressing is effected by marker-assisted selection with a genetic marker linked to the locus.
  • the marker-assisted selection comprises: (a) genotyping a plurality of plants for a marker associated with ASR tolerance; and (b) selecting a plant comprising the marker.
  • the method further comprises backcrossing the corn plant with a corn plant lacking ASR tolerance as the non-recurrent parent. In still another embodiment, the backcrossing is performed 2-10 generations.
  • genetic markers according to the invention may be selected from the group consisting of TIDP7054, umc2124a, les22, IDP1489, TIDP6496, dupssr26, umc2228, IDP4988, IDP252, IDP9114, IDP9114, SEQ ID NO:l, bnlg2295, IMR18, TIDP8768, gpm305, SEQ ID NO:2, TIDP7103, IDP5866, SEQ ID NO:3, IDP4792, SEQ ID NO:4, TIDP7049, SEQ ID NO:5, TIDP4596, SEQ ID NO:6, TIDP9243, umcl515, umc2230, SEQ ID NO:7, SEQ ID NO:8, TIDP5625, pco076392, umcl469, SEQ ID NO:9, TIDP8792, SEQ ID NO: 10, IDP1407, SEQ ID NO: 11, IDP8606, SEQ ID
  • the locus is further defined as located within a chromosome interval flanked by pairs of markers selected from the group consisting of: umc2228 and IDP451, umc2228 and haclOlb, SEQ ID NO: 2 and IDP637, and umcl515 and IDP1407.
  • the locus is located within 10 cM of said markers TIDP7054 and AY104360.
  • the corn plant lacking the locus is an agronomically elite corn line.
  • the agronomically elite corn plant is an inbred or a hybrid.
  • the locus is introgressed from an inbred or from a hybrid.
  • the invention provides a method for plant breeding comprising: (a) crossing a first corn plant lacking a locus associated with anthracnose stalk rot (ASR) tolerance with a second plant comprising the locus associated with ASR tolerance, wherein the locus is defined as flanked by markers TIDP7054 and AY104360; and (b) selecting progeny comprising a marker within the locus associated with ASR.
  • the method further comprises: (c) crossing the selected progeny with itself or a third plant to produce seed of a subsequent progeny plant; and (d) repeating step (b).
  • the method further comprises repeating steps (c) and (d) for 2-10 generations to produce a further progeny plant.
  • the method further comprises crossing the further progeny plant with a second distinct corn plant.
  • the invention provides a method of identifying an anthracnose stalk rot (ASR) tolerant plant comprising genotyping a plurality of plants for a marker associated with ASR tolerance, wherein said marker is located within a locus defined as flanked by markers TIDP7054 and AY104360 and identifying a plant comprising said marker that is ASR tolerant.
  • ASR anthracnose stalk rot
  • the invention provides a progeny plant of an anthracnose stalk rot (ASR) tolerant corn plant comprising a locus associated with ASR tolerance defined as flanked by markers TIDP7054 and AY104360, produced by crossing a first corn plant lacking the locus associated with ASR tolerance with a second plant comprising the locus associated with ASR tolerance.
  • ASR anthracnose stalk rot
  • the progeny plant is an F2 - F6 progeny.
  • the invention provides corn plants, corn seeds, corn cells and corn plant parts produced by methods of the present invention.
  • plant parts may comprise for example embryos, pollen, flowers, kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers, silk, and the like.
  • corn plants may comprise progeny plants of any generation.
  • the present invention provides methods for introgression of loci conferring anthracnose stalk rot (ASR) tolerance into varieties previously lacking such a locus, thereby providing improved disease tolerance.
  • ASR can cause severe yield loss and crop failure (Dodd 1980), and is caused by Colletotrichum graminicola (Ces.) (Cg), a fungal pathogen also known to cause leaf blight in corn (Zea mays) (Palaversic et al. 2009; Jung et al. 1994).
  • New robust sources of tolerance as well as molecular markers useful for detecting and tracking ASR tolerant DNA sequences in plant populations therefore represent a significant advance in the art.
  • the invention therefore provides marker loci and quantitative trait loci (QTL) chromosome intervals that demonstrate significant co- segregation with ASR tolerance.
  • QTL quantitative trait loci
  • methods for using markers linked to the ASR-1.01 locus to detect, select, and introgress ASR tolerance are provided. This locus is within a QTL discovered on chromosome 1 of the corn genome and is associated with the expression of ASR tolerance.
  • Embodiments of this invention therefore include methods of detecting markers within and genetically linked to this locus to create and identify disease tolerant corn lines. Also provided herein are examples of markers that are useful for detecting the presence or absence of disease tolerance alleles within the locus that can be used in maker assisted selection (MAS) breeding programs to produce plants with improved tolerance to ASR infection.
  • MAS maker assisted selection
  • Genomic markers such as TIDP7054 and AY104360 can be used to define the flanks of the chromosome interval comprising the QTL linked to ASR tolerance. Having identified this position, other genomic markers may readily be used to define chromosome sub-intervals linked to ASR tolerance.
  • chromosome interval designates a contiguous linear span of genomic DNA that resides in planta on a single chromosome.
  • the term also designates any and all genomic intervals defined by any of the markers set forth in this invention.
  • the genetic elements located on a single chromosome interval are physically linked and the size of a chromosome interval is not particularly limited.
  • the genetic elements located within a single chromosome interval are genetically linked, typically with a genetic recombination distance of, for example, less than or equal to 20 cM, or alternatively, less than or equal to 10 cM. That is, two genetic elements within a single chromosome interval undergo recombination at a frequency of less than or equal to 20% or 10%, respectively.
  • the boundaries of chromosome intervals comprise markers that will be linked to the gene controlling the trait of interest, i.e. any marker that lies within a given interval, including the terminal markers that defining the boundaries of the interval, can be used as a marker for disease tolerance.
  • the intervals described herein encompass marker clusters that co-segregate with disease tolerance. The clustering of markers occurs in relatively small domains on the chromosomes, indicating the presence of a genetic locus controlling the trait of interest in those chromosome regions.
  • the interval encompasses markers that map within the interval as well as the markers that define the terminal.
  • An interval described by the terminal markers that define the endpoints of the interval will include the terminal markers and any marker localizing within that chromosome domain, whether those markers are currently known or unknown. Although it is anticipated that one skilled in the art may describe additional polymorphic sites at marker loci in and around the markers identified herein, any marker within the chromosome intervals described herein that are associated with disease tolerance fall within the scope of this claimed invention.
  • QTL Quantitative trait locus
  • a QTL can act through a single gene mechanism or by a polygenic mechanism.
  • the invention provides QTL chromosome intervals, where a QTL (or multiple QTLs) that segregates with disease tolerance is contained in those intervals. The boundaries of chromosome intervals are drawn to encompass markers that will be linked to one or more QTL.
  • the chromosome interval is drawn such that any marker that lies within that interval (including the terminal markers that define the boundaries of the interval) can be used as markers for disease tolerance.
  • Each interval comprises at least one QTL, and furthermore, may indeed comprise more than one QTL. Close proximity of multiple QTL in the same interval may obfuscate the correlation of a particular marker with a particular QTL, as one marker may demonstrate linkage to more than one QTL. Conversely, e.g. , if two markers in close proximity show co-segregation with the desired phenotypic trait, it is sometimes unclear if each of those markers identifying the same QTL or two different QTL. Regardless, knowledge of how many QTL are in a particular interval is not necessary to make or practice the invention.
  • the present invention provides a plant comprising a nucleic acid molecule selected from the group consisting of SEQ ID NO: 1-17 fragments thereof, and complements of both.
  • the present invention also provides a plant comprising the alleles of the chromosome interval linked to ASR tolerance or fragments and complements thereof as well as any plant comprising any combination of one or more disease tolerance loci selected from the group consisting of SEQ ID NOs: 1-17. Such alleles may be homozygous or heterozygous.
  • the chromosome intervals comprising markers closely linked to the ASR-1.01
  • QTL are disclosed in Table 1. Genetic map loci are represented in cM, with position zero being the first (most distal) marker known at the beginning of the chromosome on both Monsanto's internal consensus genetic map and the Neighbors 2008 maize genomic map, which is freely available to the public from the Maize GDB website and commonly used by those skilled in the art. Also disclosed in Table 1 are the physical locations of loci as they are reported on the B73 RefGen_v2 sequence public assembly by the Arizona Genomics Institute, available on the internet.
  • ⁇ cM centiMorgans
  • IcM map units of the IBM2 2008 Neighbors Genetic Map.
  • cM refers to the classical definition of a centimorgan (Haldane, 1919, J Genet, 8:299-309) wherein one cM is equal to a 1% chance that a trait at one genetic locus will be separated from a trait at another locus due to crossing over in a single generation (meaning the traits cosegregate 99% of the time during meiosis), and this definition is used herein to delineate map locations pertaining to this invention.
  • the chromosome interval associated with ASR tolerance contains SEQ ID NOs: l-17 and is flanked by the markers TIDP7054 and AY104360, which are separated by approximately 41 cM on the internally-derived genetic map.
  • This chromosome interval encompasses a marker cluster that co-segregates with ASR tolerance in the populations studied at a p-value ⁇ 0.05.
  • An example of a subinterval associated with ASR tolerance includes the interval flanked by umc2228 and haclOlb, separated by approximately 17 cM on the internally-derived genetic map, that define a chromosome interval encompassing a cluster of markers that co-segregate with ASR tolerance in the populations studied at a p-level ⁇ 0.05.
  • chromosome intervals that comprise alleles responsible for phenotypic differences between disease tolerant and disease susceptible corn lines.
  • Each chromosome interval is characterized by the genomic regions including and flanked by and including the markers TIDP7054 and AY104360 and comprise markers within or closely linked to (within 20 cM of) ASR-1.01.
  • This invention also comprises other intervals whose borders fall between, and including, those of TIDP7054 and AY104360, or any interval closely linked to those intervals.
  • markers useful for this purpose comprise the SNP markers listed in Table 1, or any marker that maps within the chromosome intervals described herein (including the termini of the intervals), or any marker linked to those markers. Such markers can be assayed simultaneously or sequentially in a single sample or population of samples. [025] Accordingly, the markers and methods of the present invention can be utilized to guide MAS or breeding maize varieties with the desired complement (set) of allelic forms of chromosome intervals associated with superior agronomic performance (tolerance, along with any other available markers for yield, disease tolerance, etc.).
  • any of the disclosed marker alleles can be introduced into a corn line via introgression, by traditional breeding (or introduced via transformation, or both) to yield a corn plant with superior agronomic performance.
  • the number of alleles associated with tolerance that can be introduced or be present in a corn plant of the present invention ranges from lto the number of alleles disclosed herein, each integer of which is incorporated herein as if explicitly recited.
  • MAS using additional markers flanking either side of the DNA locus provide further efficiency because an unlikely double recombination event would be needed to simultaneously break linkage between the locus and both markers. Moreover, using markers tightly flanking a locus, one skilled in the art of MAS can reduce linkage drag by more accurately selecting individuals that have less of the potentially deleterious donor parent DNA. Any marker linked to or among the chromosome intervals described herein could be useful and within the scope of this invention.
  • susceptible or less tolerant plants can be identified, and, e.g. , eliminated from subsequent crosses.
  • these marker loci can be introgressed into any desired genomic background, germplasm, plant, line, variety, etc. , as part of an overall MAS breeding program designed to enhance yield.
  • the invention also provides chromosome QTL intervals that find equal use in MAS to select plants that demonstrate disease tolerance or improved tolerance. Similarly, the QTL intervals can also be used to counter-select plants that are susceptible or have reduced tolerance to disease.
  • the present invention also extends to a method of making a progeny corn plant and these progeny corn plants, per se.
  • the method comprises crossing a first parent corn plant with a second corn plant and growing the female corn plant under plant growth conditions to yield corn plant progeny. Methods of crossing and growing corn plants are well within the ability of those of ordinary skill in the art.
  • Such corn plant progeny can be assayed for alleles associated with tolerance and, thereby, the desired progeny selected.
  • Such progeny plants or seed can be sold commercially for corn production, used for food, processed to obtain a desired constituent of the corn, or further utilized in subsequent rounds of breeding.
  • At least one of the first or second corn plants is a corn plant of the present invention in that it comprises at least one of the allelic forms of the markers of the present invention, such that the progeny are capable of inheriting the allele.
  • a method of the present invention is applied to at least one related corn plant such as from progenitor or descendant lines in the subject corn plants' pedigree such that inheritance of the desired tolerance allele can be traced.
  • the number of generations separating the corn plants being subject to the methods of the present invention will generally be from 1 to 20, commonly 1 to 5, and typically 1, 2, or 3 generations of separation, and quite often a direct descendant or parent of the corn plant will be subject to the method (i.e. , one generation of separation).
  • one skilled in the art can detect the presence or absence of disease tolerance genotypes in the genomes of corn plants as part of a marker assisted selection program.
  • a breeder ascertains the genotype at one or more markers for a disease tolerant parent, which contains a disease tolerance allele, and the genotype at one or more markers for a susceptible parent, which lacks the tolerance allele.
  • the markers of the present invention can be used in MAS in crosses involving elite x exotic corn lines by subjecting the segregating progeny to MAS to maintain disease tolerance alleles, or alleles associated with yield under disease conditions.
  • a breeder can then reliably track the inheritance of the tolerance alleles through subsequent populations derived from crosses between the two parents by geno typing offspring with the markers used on the parents and comparing the genotypes at those markers with those of the parents.
  • progeny that share genotypes with the disease tolerant parent can be reliably predicted to express the tolerant phenotype; progeny that share genotypes with the disease susceptible parent can be reliably predicted to express the susceptible phenotype.
  • markers flanking the locus of interest that have alleles in linkage disequilibrium with a tolerance allele at that locus may be effectively used to select for progeny plants with enhanced tolerance to disease conditions.
  • the markers described herein such as those listed in Table 1, as well as other markers genetically or physically mapped to the same chromosome interval, may be used to select for maize plants with enhanced tolerance to disease conditions.
  • a set of these markers will be used, (e.g. , 2 or more, 3 or more, 4 or more, 5 or more) in the flanking region above the gene and a similar set in the flanking region below the gene.
  • a marker within the actual gene and/or locus may also be used.
  • the parents and their progeny are screened for these sets of markers, and the markers that are polymorphic between the two parents are used for selection.
  • this allows for selection of the gene or locus genotype at the more proximal polymorphic markers and selection for the recurrent parent genotype at the more distal polymorphic markers.
  • markers actually used to practice this invention is not particularly limited and can be any marker that maps within the intervals described herein, any marker closely linked (within 10 cM) to a marker in the chromosome intervals, or any marker selected from SEQ ID NOs: 1-17 or the markers listed in Table 1. Furthermore, since there are many different types of marker detection assays known in the art, it is not intended that the type of marker detection assay used to practice this invention be limited in any way.
  • marker locus refers to a nucleotide sequence or encoded product thereof (e.g. , a protein) used as a point of reference when identifying a linked locus.
  • a marker can be derived from genomic nucleotide sequence or from expressed nucleotide sequences (e.g. , from a spliced RNA, a cDNA, etc.), or from an encoded polypeptide, and can be represented by one or more particular variant sequences, or by a consensus sequence. In another sense, a marker is an isolated variant or consensus of such a sequence.
  • the term also refers to nucleic acid sequences complementary to or flanking the marker sequences, such as nucleic acids used as probes or primer pairs capable of amplifying the marker sequence.
  • a “marker probe” is a nucleic acid sequence or molecule that can be used to identify the presence of a marker locus, e.g. , a nucleic acid probe that is complementary to a marker locus sequence.
  • a marker probe refers to a probe of any type that is able to distinguish (i.e. , genotype) the particular allele that is present at a marker locus.
  • a “marker locus” is a locus that can be used to track the presence of a second linked locus, e.g., a linked locus that encodes or contributes to expression of a phenotypic trait.
  • a marker locus can be used to monitor segregation of alleles at a locus, such as a QTL, that are genetically or physically linked to the marker locus.
  • a "marker allele,” alternatively an “allele of a marker locus” is one of a plurality of polymorphic nucleotide sequences found at a marker locus in a population that is polymorphic for the marker locus.
  • Marker also refers to nucleic acid sequences complementary to the genomic sequences, such as nucleic acids used as probes. Markers corresponding to genetic polymorphisms between members of a population can be detected by methods well- established in the art. These include, e.g.
  • PCR-based sequence specific amplification methods detection of restriction fragment length polymorphisms (RFLP), detection of isozyme markers, detection of polynucleotide polymorphisms by allele specific hybridization (ASH), detection of amplified variable sequences of the plant genome, detection of self- sustained sequence replication, detection of simple sequence repeats (SSRs), detection of single nucleotide polymorphisms (SNPs), or detection of amplified fragment length polymorphisms (AFLPs).
  • ESTs expressed sequence tags
  • SSR markers derived from EST sequences and randomly amplified polymorphic DNA (RAPD).
  • a favorable allele of a marker is the allele of the marker that co-segregates with a desired phenotype (e.g. , disease tolerance).
  • a QTL marker has a minimum of one favorable allele, although it is possible that the marker might have two or more favorable alleles found in the population. Any favorable allele of that marker can be used advantageously for the identification and construction of disease tolerant plant lines.
  • one, two, three or more favorable allele(s) of different markers are identified in, or introgressed into a plant, and can be selected for or against during MAS. Desirably, plants or germplasm are identified that have at least one such favorable allele that positively correlates with disease tolerance or improved disease tolerance.
  • a marker allele that co-segregates with disease susceptibility also finds use with the invention, since that allele can be used to identify and counter select disease susceptible plants.
  • Such an allele can be used for exclusionary purposes during breeding to identify alleles that negatively correlate with tolerance, to eliminate susceptible plants or germplasm from subsequent rounds of breeding.
  • Genetic markers are distinguishable from each other (as well as from the plurality of alleles of anyone particular marker) on the basis of polynucleotide length and/or sequence.
  • a large number of corn molecular markers are known in the art, and are published or available from various sources, such as the MaizeGDB internet resource.
  • any differentially inherited polymorphic trait (including a nucleic acid polymorphism) that segregates among progeny is a potential genetic marker.
  • one or more marker alleles are selected for in a single plant or a population of plants.
  • plants are selected that contain favorable alleles from more than one tolerance marker, or alternatively, favorable alleles from more than one tolerance marker are introgressed into a desired germplasm.
  • the identification of favorable marker alleles is germplasm-specific. The determination of which marker alleles correlate with tolerance (or susceptibility) is determined for the particular germplasm under study.
  • methods for identifying the favorable alleles are routine and well known in the art, and furthermore, that the identification and use of such favorable alleles is well within the scope of this invention.
  • identification of favorable marker alleles in plant populations other than the populations used or described herein is well within the scope of this invention.
  • methods of the invention utilize an amplification step to detect/genotype a marker locus, but amplification is not always a requirement for marker detection (e.g. Southern blotting and RFLP detection).
  • amplification/ detection methods e.g. , by performing a real time amplification reaction that detects product formation by modification of the relevant amplification primer upon incorporation into a product, incorporation of labeled nucleotides into an amplicon, or by monitoring changes in molecular rotation properties of amplicons as compared to unamplified precursors (e.g. , by fluorescence polarization).
  • amplification in the context of nucleic acid amplification, is any process whereby additional copies of a selected nucleic acid (or a transcribed form thereof) are produced.
  • an amplification based marker technology is used wherein a primer or amplification primer pair is admixed with genomic nucleic acid isolated from the first plant or germplasm, and wherein the primer or primer pair is complementary or partially complementary to at least a portion of the marker locus, and is capable of initiating DNA polymerization by a DNA polymerase using the plant genomic nucleic acid as a template.
  • the primer or primer pair is extended in a DNA polymerization reaction having a DNA polymerase and a template genomic nucleic acid to generate at least one amplicon.
  • plant RNA is the template for the amplification reaction.
  • the QTL marker is a SNP type marker
  • the detected allele is a SNP allele
  • the method of detection is allele specific hybridization (ASH).
  • RNA polymerase based amplification e.g. , by transcription
  • An "amplicon” is an amplified nucleic acid, e.g. , a nucleic acid that is produced by amplifying a template nucleic acid by any available amplification method (e.g. , PCR, LCR, transcription, or the like).
  • genomic nucleic acid is a nucleic acid that corresponds in sequence to a heritable nucleic acid in a cell. Common examples include nuclear genomic DNA and amplicons thereof.
  • a genomic nucleic acid is, in some cases, different from a spliced RNA, or a corresponding cDNA, in that the spliced RNA or cDNA is processed, e.g. , by the splicing machinery, to remove introns.
  • Genomic nucleic acids optionally comprise non-transcribed (e.g. , chromosome structural sequences, promoter regions, enhancer regions, etc. ) and/or non-translated sequences (e.g.
  • a "template nucleic acid” is a nucleic acid that serves as a template in an amplification reaction (e.g. , a polymerase based amplification reaction such as PCR, a ligase mediated amplification reaction such as LCR, a transcription reaction, or the like).
  • a template nucleic acid can be genomic in origin, or alternatively, can be derived from expressed sequences, e.g. , a cDNA or an EST. Details regarding the use of these and other amplification methods can be found in any of a variety of standard texts.
  • RNA detection and quantification using dual-labeled fluorogenic oligonucleotide probes can also be performed according to the present invention. These probes are composed of short (e.g. , 20- 25 base) oligodeoxynucleotides that are labeled with two different fluorescent dyes.
  • each probe On the 5' terminus of each probe is a reporter dye, and on the 3' terminus of each probe a quenching dye is found.
  • the oligonucleotide probe sequence is complementary to an internal target sequence present in a PCR amplicon. When the probe is intact, energy transfer occurs between the two fluorophores and emission from the reporter is quenched by the quencher by FRET. During the extension phase of PCR, the probe is cleaved by 5' nuclease activity of the polymerase used inthe reaction, thereby releasing the reporter from the oligonucleotide- quencher and producing an increase in reporter emission intensity.
  • TaqManTM probes are oligonucleotides that have a label and a quencher, where the label is released during amplification by the exonuclease action of the polymerase used in amplification, providing a real time measure of amplification during synthesis.
  • a variety ofTaqManTM reagents are commercially available, e.g. , from Applied Biosystems as well as from a variety of specialty vendors such as Biosearch Technologies.
  • the presence or absence of a molecular marker is determined simply through nucleotide sequencing of the polymorphic marker region. This method is readily adapted to high throughput analysis as are the other methods noted above, e.g. , using available high throughput sequencing methods such as sequencing by hybridization.
  • in silico methods can be used to detect the marker loci of interest.
  • the sequence of a nucleic acid comprising the marker locus of interest can be stored in a computer.
  • the desired marker locus sequence or its homolog can be identified using an appropriate nucleic acid search algorithm as provided by, for example, in such readily available programs as BLAST, or even simple word processors.
  • any of the aforementioned marker types can be employed in the context of the invention to identify chromosome intervals encompassing genetic element that contribute to superior agronomic performance (e.g., disease tolerance or improved disease tolerance).
  • oligonucleotides including probes, primers, molecular beacons, PNAs, LNAs (locked nucleic acids), etc.
  • synthetic methods for making oligonucleotides are well known.
  • oligonucleotides can be synthesized chemically according to the solid phase phosphoramidite triester method described.
  • Oligonucleotides, including modified oligonucleotides can also be ordered from a variety of commercial sources..
  • Nucleic acid probes to the marker loci can be cloned and/or synthesized. Any suitable label can be used with a probe of the invention.
  • Detectable labels suitable for use with nucleic acid probes include, for example, any composition detectable by spectroscopic, radioisotopic, photochemical, biochemical, immunochemical, electrical, optical or chemical means.
  • Useful labels include biotin for staining with labeled streptavidin conjugate, magnetic beads, fluorescent dyes, radio labels, enzymes, and colorimetric labels.
  • Other labels include ligands which bind to antibodies labeled with fluorophores, chemiluminescent agents, and enzymes.
  • a probe can also constitute radio labeled PCR primers that are used to generate a radio labeled amplicon. It is not intended that the nucleic acid probes of the invention be limited to any particular size.
  • the molecular markers of the invention are detected using a suitable PCR-based detection method, where the size or sequence of the PCR amplicon is indicative of the absence or presence of the marker (e.g. , a particular marker allele).
  • PCR primers are hybridized to the conserved regions flanking the polymorphic marker region.
  • PCR markers used to amplify a molecular marker are sometimes termed "PCR markers" or simply "markers.” It will be appreciated that, although many specific examples of primers are provided herein, suitable primers to be used with the invention can be designed using any suitable method. It is not intended that the invention be limited to any particular primer or primer pair.
  • the primers of the invention are radiolabelled, or labeled by any suitable means (e.g. , using a non-radioactive fluorescent tag), to allow for rapid visualization of the different size amplicons following an amplification reaction without any additional labeling step or visualization step.
  • the primers are not labeled, and the amplicons are visualized following their size resolution, e.g. , following agarose gel electrophoresis.
  • ethidium bromide staining of the PCR amplicons following size resolution allows visualization of the different size amplicons. It is not intended that the primers of the invention be limited to generating an amplicon of any particular size.
  • the primers used to amplify the marker loci and alleles herein are not limited to amplifying the entire region of the relevant locus.
  • the primers can generate an amplicon of any suitable length that is longer or shorter than those disclosed herein.
  • marker amplification produces an amplicon at least 20 nucleotides in length, or alternatively, at least 50 nucleotides in length, or alternatively, at least 100 nucleotides in length, or alternatively, at least 200 nucleotides in length.
  • Marker alleles in addition to those recited herein also find use with the present invention.
  • Linkage or “genetic linkage,” is used to describe the degree with which one marker locus is “associated with” another marker locus or some other locus (for example, a tolerance locus). For example, if locus A has genes “A” or “a” and locus B has genes “B” or “b” and a cross between parent 1 with AABB and parent 2 with aabb will produce four possible gametes where the genes are segregated into AB, Ab, aB and ab. The null expectation is that there will be independent equal segregation into each of the four possible genotypes, i.e. with no linkage 1 ⁇ 4 of the gametes will of each genotype.
  • linkage can be between two markers, or alternatively between a marker and a phenotype.
  • a marker locus can be associated with (linked to) a trait, e.g. , a marker locus can be associated with tolerance or improved tolerance to a plant pathogen when the marker locus is in linkage disequilibrium with the tolerance trait.
  • the degree of linkage of a molecular marker to a phenotypic trait is measured, e.g. , as a statistical probability of co- segregation of that molecular marker with the phenotype.
  • closely linked means that the marker or locus is within about 20 cM, for instance within about 10 cM, about 5 cM, about 1 cM, about 0.5 cM, or less than 0.5 cM of the identified locus associated with ASR tolerance.
  • the linkage relationship between a molecular marker and a phenotype is given is the statistical likelihood that the particular combination of a phenotype and the presence or absence of a particular marker allele is random.
  • the lower the probability score the greater the likelihood that a phenotype and a particular marker will cosegregate.
  • an acceptable probability can be any probability of less than 50% (p ⁇ 0.5).
  • a significant probability can be less than 0.25, less than 0.20, less than 0.15, or less than 0.1.
  • any marker of the invention is linked (genetically and physically) to any other marker that is at or less than 50 cM distant.
  • any marker of the invention is closely linked (genetically and physically) to any other marker that is in close proximity, e.g. , at or less than 10 cM distant.
  • Two closely linked markers on the same chromosome can be positioned 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.75, 0.5 or 0.25 cM or less from each other.
  • the further apart on a chromosome the genes reside the less likely they are to segregate together, because homologous chromosomes recombine during meiosis.
  • the further apart on a chromosome the genes reside the more likely it is that there will be a crossing over event during meiosis that will result in the marker and the DNA sequence responsible for the trait the marker is designed to track segregating separately into progeny.
  • a common measure of linkage is the frequency with which traits cosegregate.
  • Tissue samples can be taken, for example, from the endosperm, embryo, or mature/developing plant and screened with the appropriate molecular marker to rapidly determine determined which progeny contain the desired genetics.
  • Linked markers also remove the impact of environmental factors that can often influence phenotypic expression.
  • chromosomal distance is approximately proportional to the frequency of crossing over events between traits, there is an approximate physical distance that correlates with recombination frequency.
  • Marker loci are themselves traits and can be assessed according to standard linkage analysis by tracking the marker loci during segregation. Thus, in the context of the present invention, one cM is equal to a 1 % chance that a marker locus will be separated from another locus (which can be any other trait, e.g. , another marker locus, or another trait locus that encodes a QTL), due to crossing over in a single generation.
  • the "favorable” allele at the locus of interest e.g., a QTL for tolerance
  • the two "favorable” alleles are not inherited together (i.e. , the two loci are "out of phase” with each other).
  • An allele of a QTL can comprise multiple genes or other genetic factors even within a contiguous genomic region or linkage group, such as a haplotype.
  • an allele of a disease tolerance locus can encompass more than one gene or nucleotide sequence where each individual gene or nucleotide sequence is also capable of exhibiting allelic variation and where each gene or nucleotide sequence is also capable of eliciting a phenotypic effect on the quantitative trait in question.
  • the allele of a QTL comprises one or more genes or nucleic acid sequences that are also capable of exhibiting allelic variation.
  • an allele of a QTL is thus not intended to exclude a QTL that comprises more than one gene or other genetic factor.
  • an "allele of a QTL" in the present in the invention can denote a haplotype within a haplotype window wherein a phenotype can be disease tolerance.
  • a haplotype window is a contiguous genomic region that can be defined, and tracked, with a set of one or more polymorphic markers wherein the polymorphisms indicate identity by descent.
  • a haplotype within that window can be defined by the unique fingerprint of alleles at each marker.
  • an allele is one of several alternative forms of a gene occupying a given locus on a chromosome.
  • Plants of the present invention may be homozygous or heterozygous at any particular disease locus or for a particular polymorphic marker.
  • a “genetic map” is the relationship of genetic linkage among loci on one or more chromosomes (or linkage groups) within a given species, generally depicted in a diagrammatic or tabular form. "Genetic mapping” is the process of defining the linkage relationships of loci through the use of genetic markers, populations segregating for the markers, and standard genetic principles of recombination frequency.
  • a “genetic map location” is a location on a genetic map relative to surrounding genetic markers on the same linkage group where a specified marker can be found within a given species.
  • a physical map of the genome refers to absolute distances (for example, measured in base pairs or isolated and overlapping contiguous genetic fragments, e.g. , contigs).
  • a physical map of the genome does not take into account the genetic behavior (e.g. , recombination frequencies) between different points on the physical map.
  • a "genetic recombination frequency” is the frequency of a crossing over event (recombination) between two genetic loci. Recombination frequency can be observed by following the segregation of markers and/or traits following meiosis. In some cases, two different markers can have the same genetic map coordinates. In that case, the two markers are in such close proximity to each other that recombination occurs between them with such low frequency that it is undetected.
  • Genetic maps are graphical representations of genomes (or a portion of a genome such as a single chromosome) where the distances between markers are measured by the recombination frequencies between them.
  • Plant breeders use genetic maps of molecular markers to increase breeding efficiency through Marker assisted selection (MAS), a process where selection for a trait of interest is not based on the trait itself but rather on the genotype of a marker linked to the trait.
  • MAS Marker assisted selection
  • a molecular marker that demonstrates reliable linkage with a phenotypic trait provides a useful tool for indirectly selecting the trait in a plant population, especially when accurate phenotyping is difficult, slow, or expensive.
  • recombination frequencies and as a result, genetic map positions in any particular population are not static.
  • the genetic distances separating two markers can vary depending on how the map positions are determined.
  • variables such as the parental mapping populations used, the software used in the marker mapping or QTL mapping, and the parameters input by the user of the mapping software can contribute to the QTL marker genetic map relationships.
  • the invention be limited to any particular mapping populations, use of any particular software, or any particular set of software parameters to determine linkage of a particular marker or chromosome interval with the disease tolerance phenotype.
  • Association or LD mapping techniques aim to identify genotype -phenotype associations that are significant. It is effective for fine mapping in outcrossing species where frequent recombination among heterozygotes can result in rapid LD decay.
  • LD is non- random association of alleles in a collection of individuals, reflecting the recombinational history of that region.
  • LD decay averages can help determine the number of markers necessary for a genome-wide association study to generate a genetic map with a desired level of resolution.
  • Intragression refers to the transmission of a desired allele of a genetic locus from one genetic background to another by.
  • introgression of a desired allele at a specified locus can be transmitted to at least one progeny via a sexual cross between two parents of the same species, where at least one of the parents has the desired allele in its genome.
  • transmission of an allele can occur by recombination between two donor genomes, e.g. , in a fused protoplast, where at least one of the donor protoplasts has the desired allele in its genome.
  • the desired allele can be, e.g. , a selected allele of a marker, a QTL, a transgene, or the like.
  • offspring comprising the desired allele can be repeatedly backcrossed to a line having a desired genetic background and selected for the desired allele, to result in the allele becoming fixed in a selected genetic background.
  • a primary motivation for development of molecular markers in crop species is the potential for increased efficiency in plant breeding through marker assisted selection (MAS).
  • MAS marker assisted selection
  • Genetic markers are used to identify plants that contain a desired genotype at one or more loci, and that are expected to transfer the desired genotype, along with a desired phenotype to their progeny.
  • Genetic markers can be used to identify plants containing a desired genotype at one locus, or at several unlinked or linked loci (e.g. , a haplotype), and that would be expected to transfer the desired genotype, along with a desired phenotype to their progeny.
  • the present invention provides the means to identify plants that are tolerant, exhibit improved tolerance or are susceptible to ASR infection by identifying plants having a specified allele that is linked to ASR- 1.01.
  • MAS uses polymorphic markers that have been identified as having a significant likelihood of co-segregation with a tolerance trait. Such markers are presumed to map near a gene or genes that give the plant its tolerance phenotype, and are considered indicators for the desired trait, and are termed QTL markers. Plants are tested for the presence or absence of a desired allele in the QTL marker.
  • the allele that is detected is a favorable allele that positively correlates with disease tolerance or improved disease tolerance.
  • an allele is selected for each of the markers; thus, two or more alleles are selected.
  • a marker locus will have more than one advantageous allele, and in that case, either allele can be selected.
  • the ability to identify QTL marker loci alleles that correlate with tolerance, improved tolerance or susceptibility of a corn plant to disease conditions provides a method for selecting plants that have favorable marker loci as well. That is, any plant that is identified as comprising a desired marker locus (e.g. , a marker allele that positively correlates with tolerance) can be selected for, while plants that lack the locus, or that have a locus that negatively correlates with tolerance, can be selected against.
  • a disease tolerant first corn plant or germplasm (the donor) can be crossed with a second corn plant or germplasm (the recipient, e.g. , an elite or exotic corn, depending on characteristics that are desired in the progeny) to create an introgressed corn plant or germplasm as part of a breeding program designed to improve disease tolerance of the recipient corn plant or germplasm.
  • the recipient plant can also contain one or more disease tolerant loci, which can be qualitative or quantitative trait loci.
  • the recipient plant can contain a transgene.
  • the recipient corn plant or germplasm will typically display reduced tolerance to disease conditions as compared to the first corn plant or germplasm, while the introgressed corn plant or germplasm will display an increased tolerance to disease conditions as compared to the second plant or germplasm.
  • An introgressed corn plant or germplasm produced by these methods are also a feature of this invention.
  • MAS is a powerful shortcut to selecting for desired phenotypes and for introgressing desired traits into cultivars (e.g. , introgressing desired traits into elite lines). MAS is easily adapted to high throughput molecular analysis methods that can quickly screen large numbers of plant or germplasm genetic material for the markers of interest and is much more cost effective than raising and observing plants for visible traits.
  • One application of MAS is to use the tolerance or improved tolerance markers to increase the efficiency of an introgression effort aimed at introducing a tolerance QTL into a desired (typically high yielding) background. If the nucleic acids from a plant are positive for a desired genetic marker allele, the plant can be self fertilized to create a true breeding line with the same genotype, or it can be crossed with a plant with the same marker or with other characteristics to create a sexually crossed hybrid generation.
  • Another use of MAS in plant breeding is to assist the recovery of the recurrent parent genotype by backcross breeding. Backcross breeding is the process of crossing a progeny back to one of its parents or parent lines.
  • Backcrossing is usually done for the purpose of introgressing one or a few loci from a donor parent (e.g. , a parent comprising desirable tolerance marker loci) into an otherwise desirable genetic background from the recurrent parent (e.g. , an otherwise high yielding line).
  • a donor parent e.g. , a parent comprising desirable tolerance marker loci
  • an otherwise desirable genetic background e.g. , an otherwise high yielding line.
  • the more cycles of back crossing that are done the greater the genetic contribution of the recurrent parent to the resulting introgressed variety. This is often necessary, because tolerant plants may be otherwise undesirable, e.g. , due to low yield, low fecundity, or the like.
  • strains which are the result of intensive breeding programs may have excellent yield, fecundity or the like, merely being deficient in one desired trait such as tolerance to ASR infection.
  • the genetic contribution of the plant providing disease tolerance can be reduced by back-crossing or other suitable approaches.
  • the nuclear genetic material derived from the donor material in the plant can be less than or about 50%, less than or about 25%, less than or about 13%, less than or about 5%, 3%, 2% or 1%, but that the recipient remains resistant to disease.
  • Genetic diversity is important for long term genetic gain in any breeding program. With limited diversity, genetic gain will eventually plateau when all of the favorable alleles have been fixed within the elite population.
  • One objective is to incorporate diversity into an elite pool without losing the genetic gain that has already been made and with the minimum possible investment.
  • MAS provide an indication of which genomic regions and which favorable alleles from the original ancestors have been selected for and conserved over time, facilitating efforts to incorporate favorable variation from exotic germplasm sources (parents that are unrelated to the elite gene pool) in the hopes of finding favorable alleles that do not currently exist in the elite gene pool.
  • Systems including automated systems for selecting plants that comprise a marker of interest and/or for correlating presence of the marker with tolerance are also a feature of the invention. These systems can include probes relevant to marker locus detection, detectors for detecting labels on the probes, appropriate fluid handling elements and temperature controllers that mix probes and templates and/or amplify templates and systems instructions that correlate label detection to the presence of a particular marker locus or allele.
  • this invention could be used on any plant.
  • the plant is selected from the genus Zea.
  • the plant is selected from the species Zea mays.
  • the plant is selected from the subspecies Zea mays L. ssp. mays.
  • the plant is selected from the group Zea mays L. subsp. mays Indentata, otherwise known as dent corn.
  • the plant is selected from the group Zea mays L. subsp. mays Indurata, otherwise known as flint corn.
  • the plant is selected from the group Zea mays L. subsp. mays Saccharata, otherwise known as sweet corn.
  • the plant is selected from the group Zea mays L. subsp. mays Amylacea, otherwise known as flour corn.
  • the plant is selected from the group Zea mays L. subsp. mays Everta, otherwise known as pop corn.
  • Zea plants include hybrids, inbreds, partial inbreds, or members of defined or undefined populations.
  • the present invention provides a plant to be assayed for tolerance or susceptibility to disease by any method to determine whether a plant is resistant, susceptible, or whether it exhibits some degree of tolerance or susceptibility.
  • Populations of plants can be similarly characterized in this manner, or further characterized as segregating for the trait of disease tolerance.
  • a plant of the present invention may exhibit the characteristics of any relative maturity group.
  • the maturity group is selected from the group consisting of early maturing varieties, mid season maturing varieties, and full season varieties.
  • corn seed of the invention can be subjected to various treatments.
  • the seeds can be treated to improve germination by priming the seeds or by disinfection to protect against seed-born pathogens.
  • seeds can be coated with any available coating to improve, for example, plantability, seed emergence, and protection against seed-born pathogens.
  • Seed coating can be any form of seed coating including, but not limited to, pelleting, film coating, and encrustments.
  • the present invention provides bacterial, viral, microbial, insect, mammalian and plant cells comprising the nucleic acid molecules of the present invention.
  • a corn plant of the invention can show a comparative tolerance compared to a non-tolerant control corn plant.
  • a control corn plant will preferably be genetically similar except for the disease tolerance allele or alleles in question. Such plants can be grown under similar conditions with equivalent or near equivalent exposure to the pathogen.
  • Adjacent when used to describe a nucleic acid molecule that hybridizes to
  • DNA containing a polymorphism refers to a nucleic acid that hybridizes to DNA sequences that directly abut the polymorphic nucleotide base position.
  • a nucleic acid molecule that can be used in a single base extension assay is "adjacent" to the polymorphism.
  • "Allele" refers to an alternative nucleic acid sequence at a particular locus; the length of an allele can be as small as 1 nucleotide base, but is typically larger. For example, a first allele can occur on one chromosome, while a second allele occurs on a second homologous chromosome, e.g.
  • a favorable allele is the allele at a particular locus that confers, or contributes to, an agronomically desirable phenotype, or alternatively, is an allele that allows the identification of susceptible plants that can be removed from a breeding program or planting.
  • a favorable allele of a marker is a marker allele that segregates with the favorable phenotype, or alternatively, segregates with susceptible plant phenotype, therefore providing the benefit of identifying disease prone plants.
  • a favorable allelic form of a chromosome interval is a chromosome interval that includes a nucleotide sequence that contributes to superior agronomic performance at one or more genetic loci physically located on the chromosome interval.
  • Allele frequency refers to the frequency (proportion or percentage) at which an allele is present at a locus within an individual, within a line, or within a population of lines. For example, for an allele "A,” diploid individuals of genotype "AA,” “Aa,” or “aa” have allele frequencies of 1.0, 0.5, or 0.0, respectively. One can estimate the allele frequency within a line by averaging the allele frequencies of a sample of individuals from that line.
  • an allele frequency can be expressed as a count of individuals or lines (or any other specified grouping) containing the allele.
  • An allele positively correlates with a trait when it is linked to it and when presence of the allele is an indictor that the desired trait or trait form will occur in a plant comprising the allele.
  • An allele negatively correlates with a trait when it is linked to it and when presence of the allele is an indicator that a desired trait or trait form will not occur in a plant comprising the allele.
  • Cross means to produce progeny via fertilization (e.g. cells, seeds or plants) and includes crosses between plants (sexual) and self fertilization (selfing).
  • Elite line means any line that has resulted from breeding and selection for superior agronomic performance. Numerous elite lines are available and known to those of skill in the art of corn breeding. An "elite population” is an assortment of elite individuals or lines that can be used to represent the state of the art in terms of agronomically superior genotypes of a given crop species, such as corn. Similarly, an "elite germplasm” or elite strain of germplasm is an agronomically superior germplasm, typically derived from and/or capable of giving rise to a
  • Exogenous nucleic acid is a nucleic acid that is not native to a specified system (e.g. , a germplasm, plant, variety, etc.), with respect to sequence, genomic position, or both.
  • a specified system e.g. , a germplasm, plant, variety, etc.
  • the terms “exogenous” or “heterologous” as applied to polynucleotides or polypeptides typically refers to molecules that have been artificially supplied to a biological system (e.g. , a plant cell, a plant gene, a particular plant species or variety or a plant chromosome under study) and are not native to that particular biological system.
  • a "native” or “endogenous” gene is a gene that does not contain nucleic acid elements encoded by sources other than the chromosome or other genetic element on which it is normally found in nature.
  • An endogenous gene, transcript or polypeptide is encoded by its natural chromosomal locus, and not artificially supplied to the cell.
  • Gene refers to a heritable sequence of DNA, i.e. , a genomic sequence, with functional significance.
  • the term “gene” can also be used to refer to, e.g. , a cDNA and/or a mRNA encoded by a genomic sequence, as well as to that genomic sequence.
  • Genotype is the genetic constitution of an individual (or group of individuals) at one or more genetic loci, as contrasted with the observable trait (the phenotype). Genotype is defined by the allele(s) of one or more known loci that the individual has inherited from its parents. The term genotype can be used to refer to an individual's genetic constitution at a single locus, at multiple loci, or, more generally, the term genotype can be used to refer to an individual's genetic make-up for all the genes in its genome.
  • haplotype is the genotype of an individual at a plurality of genetic loci. Typically, the genetic loci described by a haplotype are physically and genetically linked, i. e.
  • phenotype refers to one or more trait of an organism.
  • the phenotype can be observable to the naked eye, or by any other means of evaluation known in the art, e.g., microscopy, biochemical analysis, genomic analysis, an assay for a particular disease tolerance, etc.
  • a phenotype is directly controlled by a single gene or genetic locus, i.e. , a "single gene trait.”
  • a phenotype is the result of several genes.
  • “Germplasm” refers to genetic material of or from an individual (e.g.
  • germplasm includes cells, seed or tissues from which new plants may be grown, or plant parts, such as leafs, stems, pollen, or cells that can be cultured into a whole plant.
  • Linkage disequilibrium refers to a non-random segregation of genetic loci or traits (or both). In either case, linkage disequilibrium implies that the relevant loci are within sufficient physical proximity along a length of a chromosome so that they segregate together with greater than random (i.e. , non-random) frequency (in the case of co-segregating traits, the loci that underlie the traits are in sufficient proximity to each other). Linked loci co- segregate more than 50% of the time, e.g. , from about 51% to about 100% of the time.
  • the tern "physically linked" is sometimes used to indicate that two loci, e.g.
  • two marker loci are physically present on the same chromosome.
  • the two linked loci are located in close proximity such that recombination between homologous chromosome pairs does not occur between the two loci during meiosis with high frequency, e.g. , such that linked loci cosegregate at least about 90% of the time, e.g., 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.75%, or more of the time.
  • Locus a chromosome region where a polymorphic nucleic acid, trait determinant, gene or marker is located.
  • the loci of this invention comprise one or more polymorphisms in a population; i.e. , alternative alleles are present in some individuals.
  • a "gene locus” is a specific chromosome location in the genome of a species where a specific gene can be found.
  • Marker Assay means a method for detecting a polymorphism at a particular locus using a particular method, e.g. measurement of at least one phenotype (such as seed color, flower color, or other visually detectable trait), restriction fragment length polymorphism (RFLP), single base extension, electrophoresis, sequence alignment, allelic specific oligonucleotide hybridization (ASO), random amplified polymorphic DNA (RAPD), microarray-based technologies, and nucleic acid sequencing technologies, etc.
  • phenotype such as seed color, flower color, or other visually detectable trait
  • RFLP restriction fragment length polymorphism
  • ASO allelic specific oligonucleotide hybridization
  • RAPD random amplified polymorphic DNA
  • microarray-based technologies e.g., microarray-based technologies, and nucleic acid sequencing technologies, etc.
  • MAS Marker Assisted Selection
  • Molecular phenotype is a phenotype detectable at the level of a population of one or more molecules. Such molecules can be nucleic acids, proteins, or metabolites. A molecular phenotype could be an expression profile for one or more gene products, e.g. , at a specific stage of plant development, in response to an environmental condition or stress, etc.
  • operably linked refers to the association of two or more nucleic acid elements in a recombinant DNA construct, e.g. as when a promoter is operably linked with DNA that is transcribed to RNA whether for expressing or suppressing a protein.
  • Recombinant DNA constructs can be designed to express a protein which can be an endogenous protein, an exogenous homologue of an endogenous protein or an exogenous protein with no native homologue.
  • recombinant DNA constructs can be designed to suppress the level of an endogenous protein, e.g. by suppression of the native gene.
  • RNAi RNA interference
  • Gene suppression can also be effected by recombinant DNA that comprises anti-sense oriented DNA matched to the gene targeted for suppression.
  • Gene suppression can also be effected by recombinant DNA that comprises DNA that is transcribed to a microRNA matched to the gene targeted for suppression.
  • Percent identity or " identity” means the extent to which two optimally aligned DNA or protein segments are invariant throughout a window of alignment of components, for example nucleotide sequence or amino acid sequence.
  • An "identity fraction” for aligned segments of a test sequence and a reference sequence is the number of identical components that are shared by sequences of the two aligned segments divided by the total number of sequence components in the reference segment over a window of alignment which is the smaller of the full test sequence or the full reference sequence.
  • Phenotype means the detectable characteristics of a cell or organism which can be influenced by genotype.
  • Plant refers to a whole plant any part thereof, or a cell or tissue culture derived from a plant, comprising any of: whole plants, plant components or organs (e.g. , leaves, stems, roots, etc.), plant tissues, seeds, plant cells, and/or progeny of the same.
  • a plant cell is a biological cell of a plant, taken from a plant or derived through culture from a cell taken from a plant.
  • Polymorphism means the presence of one or more variations in a population. A polymorphism may manifest as a variation in the nucleotide sequence of a nucleic acid or as a variation in the amino acid sequence of a protein.
  • Polymorphisms include the presence of one or more variations of a nucleic acid sequence or nucleic acid feature at one or more loci in a population of one or more individuals.
  • the variation may comprise but is not limited to one or more nucleotide base changes, the insertion of one or more nucleotides or the deletion of one or more nucleotides.
  • a polymorphism may arise from random processes in nucleic acid replication, through mutagenesis, as a result of mobile genomic elements, from copy number variation and during the process of meiosis, such as unequal crossing over, genome duplication and chromosome breaks and fusions.
  • Useful polymorphisms may include single nucleotide polymorphisms (SNPs), insertions or deletions in DNA sequence (Indels), simple sequence repeats of DNA sequence (SSRs), a restriction fragment length polymorphism, and a tag SNP.
  • SNPs single nucleotide polymorphisms
  • Indels insertions or deletions in DNA sequence
  • SSRs simple sequence repeats of DNA sequence
  • restriction fragment length polymorphism a tag SNP.
  • a genetic marker, a gene, a DNA-derived sequence, a RNA-derived sequence, a promoter, a 5' untranslated region of a gene, a 3' untranslated region of a gene, microRNA, siRNA, a tolerance locus, a satellite marker, a transgene, mRNA, ds mRNA, a transcriptional profile, and a methylation pattern may also comprise polymorphisms.
  • the presence, absence, or variation in copy number of the preceding may comprise polymorphisms.
  • a "population of plants” or "plant population” means a set comprising any number, including one, of individuals, objects, or data from which samples are taken for evaluation, e.g. estimating QTL effects. Most commonly, the terms relate to a breeding population of plants from which members are selected and crossed to produce progeny in a breeding program.
  • a population of plants can include the progeny of a single breeding cross or a plurality of breeding crosses, and can be either actual plants or plant derived material, or in silico representations of the plants.
  • the population members need not be identical to the population members selected for use in subsequent cycles of analyses or those ultimately selected to obtain final progeny plants.
  • a plant population is derived from a single biparental cross, but may also derive from two or more crosses between the same or different parents.
  • a population of plants may comprise any number of individuals, those of skill in the art will recognize that plant breeders commonly use population sizes ranging from one or two hundred individuals to several thousand, and that the highest performing 5-20% of a population is what is commonly selected to be used in subsequent crosses in order to improve the performance of subsequent generations of the population.
  • Resistance locus means a locus associated with resistance to disease.
  • a resistance locus according to the present invention may, in one embodiment, control resistance or susceptibility for one or more races of Colletotrichum graminicola.
  • Resistance allele means the nucleic acid sequence associated with resistance to disease.
  • Recombinant in reference to a nucleic acid or polypeptide indicates that the material ⁇ e.g. , a recombinant nucleic acid, gene, polynucleotide, polypeptide, etc.) has been altered by human intervention.
  • the term recombinant can also refer to an organism that harbors recombinant material, e.g. , a plant that comprises a recombinant nucleic acid is considered a recombinant plant.
  • Tolerance or "improved tolerance” in a plant to disease conditions is an indication that the plant is less affected by disease conditions with respect to yield, survivability and/or other relevant agronomic measures, compared to a less tolerant, more "susceptible" plant. Tolerance is a relative term, indicating that a "tolerant" plant survives and/or produces better yields in disease conditions compared to a different (less tolerant) plant ⁇ e.g. , a different corn line strain) grown in similar disease conditions.
  • Transgenic plant refers to a plant that comprises within its cells a heterologous polynucleotide.
  • the heterologous polynucleotide is stably integrated within the genome such that the polynucleotide is passed on to successive generations.
  • the heterologous polynucleotide may be integrated into the genome alone or as part of a recombinant expression cassette.
  • Transgenic is used herein to refer to any cell, cell line, callus, tissue, plant part or plant, the genotype of which has been altered by the presence of heterologous nucleic acid including those transgenic organisms or cells initially so altered, as well as those created by crosses or asexual propagation from the initial transgenic organism or cell.
  • transgenic does not encompass the alteration of the genome (chromosomal or extrachromosomal) by conventional plant breeding methods (e.g. , crosses) or by naturally occurring events such as random cross-fertilization, non-recombinant viral infection, non-recombinant bacterial transformation, non-recombinant transposition, or spontaneous mutation.
  • Vector is a polynucleotide or other molecule that transfers nucleic acids between cells. Vectors are often derived from plasmids, bacteriophages, or viruses and optionally comprise parts which mediate vector maintenance and enable its intended use.
  • a "cloning vector” or “shuttle vector” or “sub cloning vector” contains operably linked parts that facilitate subcloning steps (e.g. , a multiple cloning site containing multiple restriction endonuclease sites).
  • expression vector refers to a vector comprising operably linked polynucleotide sequences that facilitate expression of a coding sequence in a particular host organism (e.g. , a bacterial expression vector or a plant expression vector).
  • Yield is the culmination of all agronomic traits as determined by the productivity per unit area of a particular plant product of commercial value.
  • Agronomic traits include the underlying genetic elements of a given plant variety that contribute to yield over the course of growing season.
  • Example 1 Inoculation and assessment of ASR tolerance phenotypes.
  • Table 2 Rating Scale of relative ASR infection tolerance phenotypes.
  • Example 2 Assays useful for detecting ASR tolerance genotypes.
  • primer sequences for amplifying exemplary SNP marker loci linked to the ASR-1.01 QTL and the probes used to genotype the corresponding SNP sequences are provided in Table 3.
  • Primer and probe synthesis is within the skill of the art once the SNP position in the corn genome is provided.
  • One of skill in the art will also immediately recognize that other sequences to either side of the given primers can be used in place of the given primers, so long as the primers can amplify a region that includes the allele to be detected.
  • the precise probe to be used for detection can vary, e.g. , any probe that can identify the region of a marker amplicon to be detected can be substituted for those examples provided herein.
  • amplification primers and detection probes can, of course, vary.
  • the invention is not limited to the primers, probes, or marker sequences specifically recited herein. Table 3. Primers and probes useful for detecting ASR tolerance SNPs.
  • Illustrative ASR tolerance marker DNA sequences SEQ ID NOs:l, 10, or 15 can be amplified using the primers indicated in Table 3 using SEQ ID NOs:18 and 35, 27 and 44, or 32 and 49, respectively, and detected with probes indicated in Table 3 as SEQ ID NOs:52 and 69, 61 and 78, or 66 and 83, respectively.
  • 192 doubled-haploid plants derived from the cross of a resistant maize inbred line and a susceptible female maize inbred line were phenotyped for ASR tolerance in two field replicates at a research site in Brazil using methods described in the art and the rating scale in Example 1. These 192 plants were then genotyped using 300 SNPs that collectively spanned each chromosome in the maize genome. Loci were eliminated from further analysis in where they were monomorphic in the subject population studied.
  • Table 4 lists the effect estimates on ASR tolerance phenotype ratings associated with each marker (SEQ ID NO). Each row provides the SEQ ID NO of the marker, and the estimated effect that the marker polymorphism had on the ASR phenotype. The statistical significance (p-value) of the association between the marker and the ASR tolerance rating in each case was p-val ⁇ 0.001.
  • SEQ ID NO:3 was associated with a 0.519 change in ASR tolerance rating by one copy of the favorable allele.
  • SEQ ID NO:5 was associated with a 0.437 change in ASR tolerance rating by one copy of the favorable allele.
  • ASR tolerance ratings were generated using the methods described in Example 1.
  • Table 5 describes the profile of the ASR-1.01 QTL revealed by the CIM analysis, including the chromosome interval where the Likelihood ratio was within the threshold of p-value ⁇ 0.01. Table 5. Results of the composite interval mapping (CIM) analysis. Markers umc2228 and haclOlb are the closest markers t to the points on chromosome 1 where the CIM Likelihood ratio remained within the threshold of p- value ⁇ 0.01. The peak of the Likelihood ratio corresponds to the ASR- 1.01 locus.
  • CIM composite interval mapping
  • markers within the interval flanked by and including markers umc2228 and haclOlb were highly associated with ASR tolerance (p- value ⁇ 0.01). Markers bordering this region also find utility with this invention, but their associations with ASR tolerance tend to decrease as their locations become further removed from ASR-1.01.
  • Example 3 Detecting ASR tolerance in a population of plants and monitoring the introgression of ASR tolerance loci from one plant line into another via MAS.
  • a population of corn plants can be phenotyped using any method that gauges the effect of ASR infection on a plant trait, including the methods described herein.
  • the genotypes of the plants in the population at one or more markers that map to the chromosome intervals associated with ASR tolerance, or at one or more markers closely linked to one of those intervals, can also be determined.
  • statistical associations can then be made between the recorded phenotypes and the genotypes using a variety of methods known in the art, including those described herein.
  • genotypes of offspring derived from one or more individuals in the population can be compared to the genotypes of the parents at one or more marker loci linked to the ASR-1.01 genotypes of the parents at those same loci. Individuals that share marker genotypes with the resistant parent at one or more markers can then be selected for advancement in the breeding program. Individuals that do not share marker genotypes with the resistant parent, or individuals that do share marker genotypes with the susceptible parent, can be discarded. This process saves the laborious and time consuming process of phenotyping plants to verify which are resistant or susceptible.
  • useful markers comprise any marker that is within or genetically linked to the ASR-1.01 QTL. In other embodiments, useful markers comprise any marker that is within between publically available markers TIDP 7054 and AY104360. In other embodiments, associations are made between genotypes for one or more SNP markers that map between publically available markers TIDP 7054 and AY104360.
  • Selections and assays may be performed on single loci, or simultaneously on multiple loci.
  • a breeder skilled in the art could base advancement decisions on the genotypes of markers linked to ASR- 1.101 and genotypes of markers linked to other loci, simultaneously.
  • a breeder may require that the same plant must exhibit genotypes at one or more markers linked to ASR-1.01 and/or at one or more markers linked to any other locus in order to be advanced.
  • a single genotype at only one locus may be sufficient for advancement.
  • the introgression of one or more desired loci from a donor line into another is achieved via repeated backcrossing to a recurrent parent accompanied by selection to retain one or more ASR tolerance loci from the donor parent.
  • Markers associated with ASR tolerance are assayed in progeny and those progeny with one or more ASR tolerance markers are selected for advancement.
  • one or more markers can be assayed in the progeny to select for plants with the genotype of the agronomically elite parent. This invention anticipates that trait introgression activities will require more than one generation, wherein progeny are crossed to the recurrent (agronomically elite) parent or selfed.
  • Selections are made based on the presence of one or more ASR tolerance markers and can also be made based on the recurrent parent genotype, wherein screening is performed on a genetic marker and/or phenotype basis.
  • markers of this invention can be used in conjunction with other markers, ideally at least one on each chromosome of the corn genome, to track the introgression of ASR tolerance loci into elite germplasm.
  • at least 100 SNP markers assorted across the 10 chromosomes of corn will be useful in conjunction with the SNP molecular markers of the present invention to follow the introgression of ASR tolerance into elite germplasm.
  • SNP markers distributed every 5 centimorgans across the 10 chromosomes of the corn genetic linkage map, will be useful in conjunction with the SNP molecular markers of the present invention to follow the introgression of ASR tolerance into elite germplasm.
  • QTLs associated with ASR tolerance will be useful in conjunction with SNP molecular markers of the present invention to combine quantitative and qualitative ASR tolerance in the same plant. It is within the scope of this invention to utilize the methods and compositions for trait integration of ASR tolerance. It is contemplated by the inventors that the present invention will be useful for developing commercial varieties with ASR tolerance and an agronomically elite phenotype.
  • ASR-1.0 for example, those listed in Table 1, to select plants for ASR tolerance genotypes arising from the donor while selecting for the recipient genotypes in adjacent chromosome regions. In practice, this reduces the amount of linkage drag from the donor genome that maybe associated with undesirable agronomic properties.
  • This backcrossing procedure is implemented at any stage in line development and occurs in conjunction with breeding for superior agronomic characteristics or one or more traits of interest, including transgenic and nontransgenic traits.
  • ASR tolerance loci can be monitored for successful introgression following a cross with a susceptible parent with subsequent generations genotyped for one or more ASR tolerance loci and for one or more additional traits of interest, including transgenic and nontransgenic traits.
  • This invention can be used on populations other than those specifically described in this application without altering the methods described herein. Although different parents may have different genotypes at different markers, the method of using this invention is fundamentally identical. Parents are first phenotyped for ASR tolerance, genotyped at each marker, and then those genotypes are used to infer resistant or susceptible phenotypes in progeny derived from those parents, or in any other population where the genotypes are associated with the same phenotypes.

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Abstract

The present invention provides methods and compositions for producing elite lines of corn exhibiting Anthracnose Stalk Rot (ASR) tolerance. Also provided in the present invention are corn plants exhibiting ASR tolerance resulting from such methods, and methods for breeding corn such that the ASR tolerance traits may be transferred to a desired genetic background.

Description

TITLE OF INVENTION
METHODS OF CREATING FUNGI TOLERANT CORN PLANTS AND COMPOSITIONS THEREOF
CROSS REFERENCE TO RELATED APPLICATIONS
[001] This application claims the benefit of United States Provisional Application
No. 61/787,853, filed March 15, 2013, herein incorporated by reference in its entirety.
FIELD OF THE INVENTION
[002] The present invention relates to the field of agricultural biotechnology. More specifically, the invention involves methods for producing corn plants containing one or more markers that are associated with tolerance to fungi.
INCORPORATION OF SEQUENCE LISTING
[003] A sequence listing contained in the file named "MONS325WO.txt" which is
36,011 bytes (measured in MS-Windows®) and created on March 13, 2014, is filed electronically herewith and incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[004] Advances in molecular genetics have made it possible to select plants based on genetic markers linked to traits of interest, a process called marker-assisted selection (MAS). While breeding efforts to date have provided a number of useful corn lines and varieties with beneficial traits, there remains a need in the art for selection of varieties with further improved traits and methods for their production. In many cases, such efforts have been hampered by difficulties in identifying and using alleles conferring beneficial traits. These efforts can be confounded by the lack of definitive phenotypic assays, and other issues such as epistasis and polygenic or quantitative inheritance. In the absence of molecular tools such as MAS, it may not be practical to attempt to produce certain new genotypes of crop plants due to such challenges.
SUMMARY OF THE INVENTION
[005] In one aspect, the present invention provides a method of producing a corn plant with anthracnose stalk rot (ASR) tolerance comprising introgressing a chromosomal locus defined as flanked by markers TIDP7054 and AY104360, that is associated with ASR tolerance, wherein the locus is introgressed into a plant lacking the locus. In one embodiment, the introgressing is effected by marker-assisted selection with a genetic marker linked to the locus. In another embodiment, the marker-assisted selection comprises: (a) genotyping a plurality of plants for a marker associated with ASR tolerance; and (b) selecting a plant comprising the marker. In yet another embodiment, the method further comprises backcrossing the corn plant with a corn plant lacking ASR tolerance as the non-recurrent parent. In still another embodiment, the backcrossing is performed 2-10 generations.
[006] In certain embodiments, genetic markers according to the invention may be selected from the group consisting of TIDP7054, umc2124a, les22, IDP1489, TIDP6496, dupssr26, umc2228, IDP4988, IDP252, IDP9114, IDP9114, SEQ ID NO:l, bnlg2295, IMR18, TIDP8768, gpm305, SEQ ID NO:2, TIDP7103, IDP5866, SEQ ID NO:3, IDP4792, SEQ ID NO:4, TIDP7049, SEQ ID NO:5, TIDP4596, SEQ ID NO:6, TIDP9243, umcl515, umc2230, SEQ ID NO:7, SEQ ID NO:8, TIDP5625, pco076392, umcl469, SEQ ID NO:9, TIDP8792, SEQ ID NO: 10, IDP1407, SEQ ID NO: 11, IDP8606, SEQ ID NO: 12, SEQ ID NO:13, IDP4814, SEQ ID NO:14, umc2231, SEQ ID NO:15, IDP6975, SEQ ID NO:16, AI855190, CG694169, IDP637, IDP34, SEQ ID NO: 17, bif2, uaz276, haclOlb, umcl988, IDP451, umcll23, npi429, umcl398, and AY104360, or defined as a marker genetically linked to any such sequences. In other embodiments, the locus is further defined as located within a chromosome interval flanked by pairs of markers selected from the group consisting of: umc2228 and IDP451, umc2228 and haclOlb, SEQ ID NO: 2 and IDP637, and umcl515 and IDP1407. In another embodiment, the locus is located within 10 cM of said markers TIDP7054 and AY104360.
[007] In yet another embodiment, the corn plant lacking the locus is an agronomically elite corn line. In another embodiment, the agronomically elite corn plant is an inbred or a hybrid. In still another embodiment, the locus is introgressed from an inbred or from a hybrid.
[008] In another aspect, the invention provides a method for plant breeding comprising: (a) crossing a first corn plant lacking a locus associated with anthracnose stalk rot (ASR) tolerance with a second plant comprising the locus associated with ASR tolerance, wherein the locus is defined as flanked by markers TIDP7054 and AY104360; and (b) selecting progeny comprising a marker within the locus associated with ASR. In one embodiment, the method further comprises: (c) crossing the selected progeny with itself or a third plant to produce seed of a subsequent progeny plant; and (d) repeating step (b). In another embodiment, the method further comprises repeating steps (c) and (d) for 2-10 generations to produce a further progeny plant. In still another embodiment, the method further comprises crossing the further progeny plant with a second distinct corn plant.
[009] In yet another aspect, the invention provides a method of identifying an anthracnose stalk rot (ASR) tolerant plant comprising genotyping a plurality of plants for a marker associated with ASR tolerance, wherein said marker is located within a locus defined as flanked by markers TIDP7054 and AY104360 and identifying a plant comprising said marker that is ASR tolerant.
[010] In still another aspect, the invention provides a progeny plant of an anthracnose stalk rot (ASR) tolerant corn plant comprising a locus associated with ASR tolerance defined as flanked by markers TIDP7054 and AY104360, produced by crossing a first corn plant lacking the locus associated with ASR tolerance with a second plant comprising the locus associated with ASR tolerance. In one embodiment, the progeny plant is an F2 - F6 progeny.
[011] In yet further embodiments, the invention provides corn plants, corn seeds, corn cells and corn plant parts produced by methods of the present invention. In certain embodiments, such plant parts may comprise for example embryos, pollen, flowers, kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers, silk, and the like. In still further embodiments, corn plants may comprise progeny plants of any generation.
DETAILED DESCRIPTION OF THE INVENTION
[012] The present invention provides methods for introgression of loci conferring anthracnose stalk rot (ASR) tolerance into varieties previously lacking such a locus, thereby providing improved disease tolerance. ASR can cause severe yield loss and crop failure (Dodd 1980), and is caused by Colletotrichum graminicola (Ces.) (Cg), a fungal pathogen also known to cause leaf blight in corn (Zea mays) (Palaversic et al. 2009; Jung et al. 1994). New robust sources of tolerance as well as molecular markers useful for detecting and tracking ASR tolerant DNA sequences in plant populations therefore represent a significant advance in the art.
[013] In one embodiment, the invention therefore provides marker loci and quantitative trait loci (QTL) chromosome intervals that demonstrate significant co- segregation with ASR tolerance. In a particular embodiment, methods for using markers linked to the ASR-1.01 locus to detect, select, and introgress ASR tolerance are provided. This locus is within a QTL discovered on chromosome 1 of the corn genome and is associated with the expression of ASR tolerance. Embodiments of this invention therefore include methods of detecting markers within and genetically linked to this locus to create and identify disease tolerant corn lines. Also provided herein are examples of markers that are useful for detecting the presence or absence of disease tolerance alleles within the locus that can be used in maker assisted selection (MAS) breeding programs to produce plants with improved tolerance to ASR infection.
[014] The location in the maize genome of the disclosed QTL, markers and chromosome intervals, are referenced herein to a public maize genome map (IBM2 Neighbors 2008). Genomic markers such as TIDP7054 and AY104360 can be used to define the flanks of the chromosome interval comprising the QTL linked to ASR tolerance. Having identified this position, other genomic markers may readily be used to define chromosome sub-intervals linked to ASR tolerance.
Chromosome Intervals
[015] The term "chromosome interval" designates a contiguous linear span of genomic DNA that resides in planta on a single chromosome. The term also designates any and all genomic intervals defined by any of the markers set forth in this invention. The genetic elements located on a single chromosome interval are physically linked and the size of a chromosome interval is not particularly limited. In some aspects, the genetic elements located within a single chromosome interval are genetically linked, typically with a genetic recombination distance of, for example, less than or equal to 20 cM, or alternatively, less than or equal to 10 cM. That is, two genetic elements within a single chromosome interval undergo recombination at a frequency of less than or equal to 20% or 10%, respectively.
[016] The boundaries of chromosome intervals comprise markers that will be linked to the gene controlling the trait of interest, i.e. any marker that lies within a given interval, including the terminal markers that defining the boundaries of the interval, can be used as a marker for disease tolerance. The intervals described herein encompass marker clusters that co-segregate with disease tolerance. The clustering of markers occurs in relatively small domains on the chromosomes, indicating the presence of a genetic locus controlling the trait of interest in those chromosome regions. The interval encompasses markers that map within the interval as well as the markers that define the terminal.
[017] An interval described by the terminal markers that define the endpoints of the interval will include the terminal markers and any marker localizing within that chromosome domain, whether those markers are currently known or unknown. Although it is anticipated that one skilled in the art may describe additional polymorphic sites at marker loci in and around the markers identified herein, any marker within the chromosome intervals described herein that are associated with disease tolerance fall within the scope of this claimed invention.
[018] "Quantitative trait loci" or a "quantitative trait locus" (QTL) is a genetic domain that effects a phenotype that can be described in quantitative terms and can be assigned a "phenotypic value" which corresponds to a quantitative value for the phenotypic trait. A QTL can act through a single gene mechanism or by a polygenic mechanism. In some aspects, the invention provides QTL chromosome intervals, where a QTL (or multiple QTLs) that segregates with disease tolerance is contained in those intervals. The boundaries of chromosome intervals are drawn to encompass markers that will be linked to one or more QTL. In other words, the chromosome interval is drawn such that any marker that lies within that interval (including the terminal markers that define the boundaries of the interval) can be used as markers for disease tolerance. Each interval comprises at least one QTL, and furthermore, may indeed comprise more than one QTL. Close proximity of multiple QTL in the same interval may obfuscate the correlation of a particular marker with a particular QTL, as one marker may demonstrate linkage to more than one QTL. Conversely, e.g. , if two markers in close proximity show co-segregation with the desired phenotypic trait, it is sometimes unclear if each of those markers identifying the same QTL or two different QTL. Regardless, knowledge of how many QTL are in a particular interval is not necessary to make or practice the invention.
[019] The present invention provides a plant comprising a nucleic acid molecule selected from the group consisting of SEQ ID NO: 1-17 fragments thereof, and complements of both. The present invention also provides a plant comprising the alleles of the chromosome interval linked to ASR tolerance or fragments and complements thereof as well as any plant comprising any combination of one or more disease tolerance loci selected from the group consisting of SEQ ID NOs: 1-17. Such alleles may be homozygous or heterozygous. [020] The chromosome intervals comprising markers closely linked to the ASR-1.01
QTL are disclosed in Table 1. Genetic map loci are represented in cM, with position zero being the first (most distal) marker known at the beginning of the chromosome on both Monsanto's internal consensus genetic map and the Neighbors 2008 maize genomic map, which is freely available to the public from the Maize GDB website and commonly used by those skilled in the art. Also disclosed in Table 1 are the physical locations of loci as they are reported on the B73 RefGen_v2 sequence public assembly by the Arizona Genomics Institute, available on the internet.
Table 1. Genetic and physical map positions of markers and chromosome intervals associated with ASR-1.01.
Figure imgf000007_0001
TIDP9243 116.9 428.6 AC205540.3 97,667,651 97,670,906 umcl515 117.3 430.6 -- -- -- umc2230 117.7 432.4 AC203178.3 103,311,427 103,311,831
SEQ ID NO. 7 118.0 435.0 -- -- --
SEQ ID NO. 8 118.0 435.0 -- -- --
TIDP5625 118.1 433.7 AC214051.4 104,607,978 104,610,652 pco076392 118.2 434.2
ASR-1.01 118.3 434.8 -- -- -- umcl469 118.4 435.1 -- -- --
SEQ ID NO. 9 118.5 438.1 -- -- --
TIDP8792 118.6 436.0 AC194369.3 111,277,426 111,279,125
SEQ ID NO. 10 118.7 439.3 -- -- --
IDP1407 119.3 443.9 AC203280.3 119,999,096 119,999,945
SEQ ID NO. 11 119.7 439.5 -- -- --
IDP8606 120.0 449.2 AC196058.3 154,042,149 154,045,503
SEQ ID NO. 12 120.2 450.8 -- -- --
SEQ ID NO. 13 120.2 450.8 -- -- --
IDP4814 120.4 451.9 AC 194905.2 148,235,556 148,236,361
SEQ ID NO. 14 120.7 454.5 -- -- -- umc2231 120.8 453.5 AC213759.3 156,217,009 156,217,580
SEQ ID NO. 15 122.7 469.4 -- -- --
IDP6975 123.0 470.2 AC191049.3 165,083,322 165,086,168
SEQ ID NO. 16 123.1 468.3 -- -- --
AI855190 123.1 464.7 AC206254.3 164,090,469 164,091,279
CG694169 123.2 470.6 -- -- --
IDP637 123.3 465.4 AC214142.3 172,020,872 172,022,323
IDP34 123.4 465.9 AC209336.3 167,030,987 167,032,710
SEQ ID NO. 17 124.1 480.3 -- -- -- bif2 124.6 486.1 -- -- -- uaz276 124.6 485.9 AC 186423.3 173,281,068 173,281,901 haclOlb 125.1 481.9 -- -- -- umcl988 128.2 504.9 -- -- --
IDP451 128.4 505.5 AC214142.3 172,022,115 172,022,410 umcl l23 137.2 535.1 AC234203.4 188,014,690 188,015,150 npi429 137.3 535.3 -- -- -- umcl398 139.1 540.9 -- -- --
AY 104360 139.2 541.3 AC 186691.4 189,354,230 189,356,767
† cM = centiMorgans, IcM = map units of the IBM2 2008 Neighbors Genetic Map.
††Arizona Genomics Institute B73 RefGen_v2 sequence.
* Exact coordinates not known. Coordinates can be estimated based on nearest flanking loci with known coordinates. [021] In Table 1, "IcM" refers to the map units of the IBM2 2008 Neighbors Genetic
Map, which was generated with an intermated recombinant inbred population (syn 4) that resulted in approximately a four-fold increase in the number of meiosies as compared to the typical recombination experiment that is used to generate centiMorgan (cM) distances (Lee et al, 2002, Plant Mol Biol 48:453 and the Maize Genetics and Genomics Database). "cM" refers to the classical definition of a centimorgan (Haldane, 1919, J Genet, 8:299-309) wherein one cM is equal to a 1% chance that a trait at one genetic locus will be separated from a trait at another locus due to crossing over in a single generation (meaning the traits cosegregate 99% of the time during meiosis), and this definition is used herein to delineate map locations pertaining to this invention.
[022] In one embodiment, the chromosome interval associated with ASR tolerance contains SEQ ID NOs: l-17 and is flanked by the markers TIDP7054 and AY104360, which are separated by approximately 41 cM on the internally-derived genetic map. This chromosome interval encompasses a marker cluster that co-segregates with ASR tolerance in the populations studied at a p-value < 0.05. An example of a subinterval associated with ASR tolerance includes the interval flanked by umc2228 and haclOlb, separated by approximately 17 cM on the internally-derived genetic map, that define a chromosome interval encompassing a cluster of markers that co-segregate with ASR tolerance in the populations studied at a p-level < 0.05.
[023] Thus, one skilled in the art can use this invention to improve the efficiency of breeding for improved disease tolerance in maize by associating disease tolerance phenotypes with genotypes at previously unknown disease tolerance loci in the maize genome. Disclosed herein are chromosome intervals that comprise alleles responsible for phenotypic differences between disease tolerant and disease susceptible corn lines. Each chromosome interval is characterized by the genomic regions including and flanked by and including the markers TIDP7054 and AY104360 and comprise markers within or closely linked to (within 20 cM of) ASR-1.01. This invention also comprises other intervals whose borders fall between, and including, those of TIDP7054 and AY104360, or any interval closely linked to those intervals.
[024] Examples of markers useful for this purpose comprise the SNP markers listed in Table 1, or any marker that maps within the chromosome intervals described herein (including the termini of the intervals), or any marker linked to those markers. Such markers can be assayed simultaneously or sequentially in a single sample or population of samples. [025] Accordingly, the markers and methods of the present invention can be utilized to guide MAS or breeding maize varieties with the desired complement (set) of allelic forms of chromosome intervals associated with superior agronomic performance (tolerance, along with any other available markers for yield, disease tolerance, etc.). Any of the disclosed marker alleles can be introduced into a corn line via introgression, by traditional breeding (or introduced via transformation, or both) to yield a corn plant with superior agronomic performance. The number of alleles associated with tolerance that can be introduced or be present in a corn plant of the present invention ranges from lto the number of alleles disclosed herein, each integer of which is incorporated herein as if explicitly recited.
[026] MAS using additional markers flanking either side of the DNA locus provide further efficiency because an unlikely double recombination event would be needed to simultaneously break linkage between the locus and both markers. Moreover, using markers tightly flanking a locus, one skilled in the art of MAS can reduce linkage drag by more accurately selecting individuals that have less of the potentially deleterious donor parent DNA. Any marker linked to or among the chromosome intervals described herein could be useful and within the scope of this invention.
[027] Similarly, by identifying plants lacking the desired marker locus, susceptible or less tolerant plants can be identified, and, e.g. , eliminated from subsequent crosses. Similarly, these marker loci can be introgressed into any desired genomic background, germplasm, plant, line, variety, etc. , as part of an overall MAS breeding program designed to enhance yield. The invention also provides chromosome QTL intervals that find equal use in MAS to select plants that demonstrate disease tolerance or improved tolerance. Similarly, the QTL intervals can also be used to counter-select plants that are susceptible or have reduced tolerance to disease.
[028] The present invention also extends to a method of making a progeny corn plant and these progeny corn plants, per se. The method comprises crossing a first parent corn plant with a second corn plant and growing the female corn plant under plant growth conditions to yield corn plant progeny. Methods of crossing and growing corn plants are well within the ability of those of ordinary skill in the art. Such corn plant progeny can be assayed for alleles associated with tolerance and, thereby, the desired progeny selected. Such progeny plants or seed can be sold commercially for corn production, used for food, processed to obtain a desired constituent of the corn, or further utilized in subsequent rounds of breeding. At least one of the first or second corn plants is a corn plant of the present invention in that it comprises at least one of the allelic forms of the markers of the present invention, such that the progeny are capable of inheriting the allele.
[029] Often, a method of the present invention is applied to at least one related corn plant such as from progenitor or descendant lines in the subject corn plants' pedigree such that inheritance of the desired tolerance allele can be traced. The number of generations separating the corn plants being subject to the methods of the present invention will generally be from 1 to 20, commonly 1 to 5, and typically 1, 2, or 3 generations of separation, and quite often a direct descendant or parent of the corn plant will be subject to the method (i.e. , one generation of separation).
[030] Thus, with this invention, one skilled in the art can detect the presence or absence of disease tolerance genotypes in the genomes of corn plants as part of a marker assisted selection program. In one embodiment, a breeder ascertains the genotype at one or more markers for a disease tolerant parent, which contains a disease tolerance allele, and the genotype at one or more markers for a susceptible parent, which lacks the tolerance allele. For example, the markers of the present invention can be used in MAS in crosses involving elite x exotic corn lines by subjecting the segregating progeny to MAS to maintain disease tolerance alleles, or alleles associated with yield under disease conditions. A breeder can then reliably track the inheritance of the tolerance alleles through subsequent populations derived from crosses between the two parents by geno typing offspring with the markers used on the parents and comparing the genotypes at those markers with those of the parents. Depending on how tightly linked the marker alleles are with the trait, progeny that share genotypes with the disease tolerant parent can be reliably predicted to express the tolerant phenotype; progeny that share genotypes with the disease susceptible parent can be reliably predicted to express the susceptible phenotype. Thus, the laborious and inefficient process of manually phenotyping the progeny for disease tolerance is avoided.
[031] By providing the positions in the maize genome of the intervals and the disease tolerance associated markers within, this invention also allows one skilled in the art to identify other markers within the intervals disclosed herein or linked to the chromosome intervals disclosed herein.
[032] Closely linked markers flanking the locus of interest that have alleles in linkage disequilibrium with a tolerance allele at that locus may be effectively used to select for progeny plants with enhanced tolerance to disease conditions. Thus, the markers described herein, such as those listed in Table 1, as well as other markers genetically or physically mapped to the same chromosome interval, may be used to select for maize plants with enhanced tolerance to disease conditions. Typically, a set of these markers will be used, (e.g. , 2 or more, 3 or more, 4 or more, 5 or more) in the flanking region above the gene and a similar set in the flanking region below the gene. Optionally, as described above, a marker within the actual gene and/or locus may also be used. The parents and their progeny are screened for these sets of markers, and the markers that are polymorphic between the two parents are used for selection. In an introgression program, this allows for selection of the gene or locus genotype at the more proximal polymorphic markers and selection for the recurrent parent genotype at the more distal polymorphic markers.
[033] The choice of markers actually used to practice this invention is not particularly limited and can be any marker that maps within the intervals described herein, any marker closely linked (within 10 cM) to a marker in the chromosome intervals, or any marker selected from SEQ ID NOs: 1-17 or the markers listed in Table 1. Furthermore, since there are many different types of marker detection assays known in the art, it is not intended that the type of marker detection assay used to practice this invention be limited in any way.
Molecular Genetic Markers
[034] "Marker," "genetic marker," "molecular marker," "marker nucleic acid," and
"marker locus" refer to a nucleotide sequence or encoded product thereof (e.g. , a protein) used as a point of reference when identifying a linked locus. A marker can be derived from genomic nucleotide sequence or from expressed nucleotide sequences (e.g. , from a spliced RNA, a cDNA, etc.), or from an encoded polypeptide, and can be represented by one or more particular variant sequences, or by a consensus sequence. In another sense, a marker is an isolated variant or consensus of such a sequence. The term also refers to nucleic acid sequences complementary to or flanking the marker sequences, such as nucleic acids used as probes or primer pairs capable of amplifying the marker sequence. A "marker probe" is a nucleic acid sequence or molecule that can be used to identify the presence of a marker locus, e.g. , a nucleic acid probe that is complementary to a marker locus sequence. Alternatively, in some aspects, a marker probe refers to a probe of any type that is able to distinguish (i.e. , genotype) the particular allele that is present at a marker locus. A "marker locus" is a locus that can be used to track the presence of a second linked locus, e.g., a linked locus that encodes or contributes to expression of a phenotypic trait. For example, a marker locus can be used to monitor segregation of alleles at a locus, such as a QTL, that are genetically or physically linked to the marker locus. Thus, a "marker allele," alternatively an "allele of a marker locus" is one of a plurality of polymorphic nucleotide sequences found at a marker locus in a population that is polymorphic for the marker locus.
[035] "Marker" also refers to nucleic acid sequences complementary to the genomic sequences, such as nucleic acids used as probes. Markers corresponding to genetic polymorphisms between members of a population can be detected by methods well- established in the art. These include, e.g. , PCR-based sequence specific amplification methods, detection of restriction fragment length polymorphisms (RFLP), detection of isozyme markers, detection of polynucleotide polymorphisms by allele specific hybridization (ASH), detection of amplified variable sequences of the plant genome, detection of self- sustained sequence replication, detection of simple sequence repeats (SSRs), detection of single nucleotide polymorphisms (SNPs), or detection of amplified fragment length polymorphisms (AFLPs). Well established methods are also know for the detection of expressed sequence tags (ESTs) and SSR markers derived from EST sequences and randomly amplified polymorphic DNA (RAPD).
[036] A favorable allele of a marker is the allele of the marker that co-segregates with a desired phenotype (e.g. , disease tolerance). As used herein, a QTL marker has a minimum of one favorable allele, although it is possible that the marker might have two or more favorable alleles found in the population. Any favorable allele of that marker can be used advantageously for the identification and construction of disease tolerant plant lines. Optionally, one, two, three or more favorable allele(s) of different markers are identified in, or introgressed into a plant, and can be selected for or against during MAS. Desirably, plants or germplasm are identified that have at least one such favorable allele that positively correlates with disease tolerance or improved disease tolerance. Alternatively, a marker allele that co-segregates with disease susceptibility also finds use with the invention, since that allele can be used to identify and counter select disease susceptible plants. Such an allele can be used for exclusionary purposes during breeding to identify alleles that negatively correlate with tolerance, to eliminate susceptible plants or germplasm from subsequent rounds of breeding.
[037] The more tightly linked a marker is with a DNA locus influencing a phenotype, the more reliable the marker is in MAS, as the likelihood of a recombination event unlinking the marker and the locus decreases. Markers containing the causal mutation for a trait, or that are within the coding sequence of a causative gene, are ideal as no recombination is expected between them and the sequence of DNA responsible for the phenotype.
[038] Genetic markers are distinguishable from each other (as well as from the plurality of alleles of anyone particular marker) on the basis of polynucleotide length and/or sequence. A large number of corn molecular markers are known in the art, and are published or available from various sources, such as the MaizeGDB internet resource. In general, any differentially inherited polymorphic trait (including a nucleic acid polymorphism) that segregates among progeny is a potential genetic marker.
[039] In some embodiments of the invention, one or more marker alleles are selected for in a single plant or a population of plants. In these methods, plants are selected that contain favorable alleles from more than one tolerance marker, or alternatively, favorable alleles from more than one tolerance marker are introgressed into a desired germplasm. One of skill recognizes that the identification of favorable marker alleles is germplasm-specific. The determination of which marker alleles correlate with tolerance (or susceptibility) is determined for the particular germplasm under study. One of skill recognizes that methods for identifying the favorable alleles are routine and well known in the art, and furthermore, that the identification and use of such favorable alleles is well within the scope of this invention. Furthermore still, identification of favorable marker alleles in plant populations other than the populations used or described herein is well within the scope of this invention.
Marker Detection
[040] In some aspects, methods of the invention utilize an amplification step to detect/genotype a marker locus, but amplification is not always a requirement for marker detection (e.g. Southern blotting and RFLP detection). Separate detection probes can also be omitted in amplification/ detection methods, e.g. , by performing a real time amplification reaction that detects product formation by modification of the relevant amplification primer upon incorporation into a product, incorporation of labeled nucleotides into an amplicon, or by monitoring changes in molecular rotation properties of amplicons as compared to unamplified precursors (e.g. , by fluorescence polarization).
[041] "Amplifying," in the context of nucleic acid amplification, is any process whereby additional copies of a selected nucleic acid (or a transcribed form thereof) are produced. In some embodiments, an amplification based marker technology is used wherein a primer or amplification primer pair is admixed with genomic nucleic acid isolated from the first plant or germplasm, and wherein the primer or primer pair is complementary or partially complementary to at least a portion of the marker locus, and is capable of initiating DNA polymerization by a DNA polymerase using the plant genomic nucleic acid as a template. The primer or primer pair is extended in a DNA polymerization reaction having a DNA polymerase and a template genomic nucleic acid to generate at least one amplicon. In other embodiments, plant RNA is the template for the amplification reaction. In some embodiments, the QTL marker is a SNP type marker, and the detected allele is a SNP allele, and the method of detection is allele specific hybridization (ASH).
[042] In general, the majority of genetic markers rely on one or more property of nucleic acids for their detection. Typical amplification methods include various polymerase based replication methods, including the polymerase chain reaction (PCR), ligase mediated methods such as the ligase chain reaction (LCR) and RNA polymerase based amplification (e.g. , by transcription) methods. An "amplicon" is an amplified nucleic acid, e.g. , a nucleic acid that is produced by amplifying a template nucleic acid by any available amplification method (e.g. , PCR, LCR, transcription, or the like). A "genomic nucleic acid" is a nucleic acid that corresponds in sequence to a heritable nucleic acid in a cell. Common examples include nuclear genomic DNA and amplicons thereof. A genomic nucleic acid is, in some cases, different from a spliced RNA, or a corresponding cDNA, in that the spliced RNA or cDNA is processed, e.g. , by the splicing machinery, to remove introns. Genomic nucleic acids optionally comprise non-transcribed (e.g. , chromosome structural sequences, promoter regions, enhancer regions, etc. ) and/or non-translated sequences (e.g. , introns), whereas spliced RNA/cDNA typically do not have non-transcribed sequences or introns. A "template nucleic acid" is a nucleic acid that serves as a template in an amplification reaction (e.g. , a polymerase based amplification reaction such as PCR, a ligase mediated amplification reaction such as LCR, a transcription reaction, or the like). A template nucleic acid can be genomic in origin, or alternatively, can be derived from expressed sequences, e.g. , a cDNA or an EST. Details regarding the use of these and other amplification methods can be found in any of a variety of standard texts. Many available biology texts also have extended discussions regarding PCR and related amplification methods and one of skill will appreciate that essentially any RNA can be converted into a double stranded DNA suitable for restriction digestion, PCR expansion and sequencing using reverse transcriptase and a polymerase. [043] PCR detection and quantification using dual-labeled fluorogenic oligonucleotide probes, commonly referred to as "TaqManTM" probes, can also be performed according to the present invention. These probes are composed of short (e.g. , 20- 25 base) oligodeoxynucleotides that are labeled with two different fluorescent dyes. On the 5' terminus of each probe is a reporter dye, and on the 3' terminus of each probe a quenching dye is found. The oligonucleotide probe sequence is complementary to an internal target sequence present in a PCR amplicon. When the probe is intact, energy transfer occurs between the two fluorophores and emission from the reporter is quenched by the quencher by FRET. During the extension phase of PCR, the probe is cleaved by 5' nuclease activity of the polymerase used inthe reaction, thereby releasing the reporter from the oligonucleotide- quencher and producing an increase in reporter emission intensity. TaqMan™ probes are oligonucleotides that have a label and a quencher, where the label is released during amplification by the exonuclease action of the polymerase used in amplification, providing a real time measure of amplification during synthesis. A variety ofTaqMan™ reagents are commercially available, e.g. , from Applied Biosystems as well as from a variety of specialty vendors such as Biosearch Technologies.
[044] In one embodiment, the presence or absence of a molecular marker is determined simply through nucleotide sequencing of the polymorphic marker region. This method is readily adapted to high throughput analysis as are the other methods noted above, e.g. , using available high throughput sequencing methods such as sequencing by hybridization.
[045] In alternative embodiments, in silico methods can be used to detect the marker loci of interest. For example, the sequence of a nucleic acid comprising the marker locus of interest can be stored in a computer. The desired marker locus sequence or its homolog can be identified using an appropriate nucleic acid search algorithm as provided by, for example, in such readily available programs as BLAST, or even simple word processors.
[046] While the exemplary markers provided in the figures and tables herein are either SNP markers, any of the aforementioned marker types can be employed in the context of the invention to identify chromosome intervals encompassing genetic element that contribute to superior agronomic performance (e.g., disease tolerance or improved disease tolerance). Probes and Primers
[047] In general, synthetic methods for making oligonucleotides, including probes, primers, molecular beacons, PNAs, LNAs (locked nucleic acids), etc. , are well known. For example, oligonucleotides can be synthesized chemically according to the solid phase phosphoramidite triester method described. Oligonucleotides, including modified oligonucleotides, can also be ordered from a variety of commercial sources..
[048] Nucleic acid probes to the marker loci can be cloned and/or synthesized. Any suitable label can be used with a probe of the invention. Detectable labels suitable for use with nucleic acid probes include, for example, any composition detectable by spectroscopic, radioisotopic, photochemical, biochemical, immunochemical, electrical, optical or chemical means. Useful labels include biotin for staining with labeled streptavidin conjugate, magnetic beads, fluorescent dyes, radio labels, enzymes, and colorimetric labels. Other labels include ligands which bind to antibodies labeled with fluorophores, chemiluminescent agents, and enzymes. A probe can also constitute radio labeled PCR primers that are used to generate a radio labeled amplicon. It is not intended that the nucleic acid probes of the invention be limited to any particular size.
[049] In some embodiments, the molecular markers of the invention are detected using a suitable PCR-based detection method, where the size or sequence of the PCR amplicon is indicative of the absence or presence of the marker (e.g. , a particular marker allele). In these types of methods, PCR primers are hybridized to the conserved regions flanking the polymorphic marker region. As used in the art, PCR primers used to amplify a molecular marker are sometimes termed "PCR markers" or simply "markers." It will be appreciated that, although many specific examples of primers are provided herein, suitable primers to be used with the invention can be designed using any suitable method. It is not intended that the invention be limited to any particular primer or primer pair. In some embodiments, the primers of the invention are radiolabelled, or labeled by any suitable means (e.g. , using a non-radioactive fluorescent tag), to allow for rapid visualization of the different size amplicons following an amplification reaction without any additional labeling step or visualization step. In some embodiments, the primers are not labeled, and the amplicons are visualized following their size resolution, e.g. , following agarose gel electrophoresis. In some embodiments, ethidium bromide staining of the PCR amplicons following size resolution allows visualization of the different size amplicons. It is not intended that the primers of the invention be limited to generating an amplicon of any particular size. For example, the primers used to amplify the marker loci and alleles herein are not limited to amplifying the entire region of the relevant locus. The primers can generate an amplicon of any suitable length that is longer or shorter than those disclosed herein. In some embodiments, marker amplification produces an amplicon at least 20 nucleotides in length, or alternatively, at least 50 nucleotides in length, or alternatively, at least 100 nucleotides in length, or alternatively, at least 200 nucleotides in length. Marker alleles in addition to those recited herein also find use with the present invention.
Linkage Analysis
[050] "Linkage", or "genetic linkage," is used to describe the degree with which one marker locus is "associated with" another marker locus or some other locus (for example, a tolerance locus). For example, if locus A has genes "A" or "a" and locus B has genes "B" or "b" and a cross between parent 1 with AABB and parent 2 with aabb will produce four possible gametes where the genes are segregated into AB, Ab, aB and ab. The null expectation is that there will be independent equal segregation into each of the four possible genotypes, i.e. with no linkage ¼ of the gametes will of each genotype. Segregation of gametes into a genotypes differing from ¼ is attributed to linkage. As used herein, linkage can be between two markers, or alternatively between a marker and a phenotype. A marker locus can be associated with (linked to) a trait, e.g. , a marker locus can be associated with tolerance or improved tolerance to a plant pathogen when the marker locus is in linkage disequilibrium with the tolerance trait. The degree of linkage of a molecular marker to a phenotypic trait (e.g. , a QTL) is measured, e.g. , as a statistical probability of co- segregation of that molecular marker with the phenotype.
[051] As used herein, "closely linked" means that the marker or locus is within about 20 cM, for instance within about 10 cM, about 5 cM, about 1 cM, about 0.5 cM, or less than 0.5 cM of the identified locus associated with ASR tolerance.
[052] As used herein, the linkage relationship between a molecular marker and a phenotype is given is the statistical likelihood that the particular combination of a phenotype and the presence or absence of a particular marker allele is random. Thus, the lower the probability score, the greater the likelihood that a phenotype and a particular marker will cosegregate. In some embodiments, a probability score of 0.05 (p=0.05, or a 5% probability) of random assortment is considered a significant indication of co-segregation. However, the present invention is not limited to this particular standard, and an acceptable probability can be any probability of less than 50% (p< 0.5). For example, a significant probability can be less than 0.25, less than 0.20, less than 0.15, or less than 0.1. The phrase "closely linked," in the present application, means that recombination between two linked loci occurs with a frequency of equal to or less than about 10% (i.e. , are separated on a genetic map by not more than 10 cM). In one aspect, any marker of the invention is linked (genetically and physically) to any other marker that is at or less than 50 cM distant. In another aspect, any marker of the invention is closely linked (genetically and physically) to any other marker that is in close proximity, e.g. , at or less than 10 cM distant. Two closely linked markers on the same chromosome can be positioned 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.75, 0.5 or 0.25 cM or less from each other.
[053] Classical linkage analysis can be thought of as a statistical description of the relative frequencies of cosegregation of different traits. Linkage analysis is the well characterized descriptive framework of how traits are grouped together based upon the frequency with which they segregate together. That is, if two non-allelic traits are inherited together with a greater than random frequency, they are said to be "linked." The frequency with which the traits are inherited together is the primary measure of how tightly the traits are linked, i.e. , traits which are inherited together with a higher frequency are more closely linked than traits which are inherited together with lower (but still above random) frequency. The further apart on a chromosome the genes reside, the less likely they are to segregate together, because homologous chromosomes recombine during meiosis. Thus, the further apart on a chromosome the genes reside, the more likely it is that there will be a crossing over event during meiosis that will result in the marker and the DNA sequence responsible for the trait the marker is designed to track segregating separately into progeny. A common measure of linkage is the frequency with which traits cosegregate.
[054] Linkage analysis is used to determine which polymorphic marker allele demonstrates a statistical likelihood of co-segregation with the tolerance phenotype (thus, a "tolerance marker allele"). Following identification of a marker allele for co- segregation with the tolerance phenotype, it is possible to use this marker for rapid, accurate screening of plant lines for the tolerance allele without the need to grow the plants through their life cycle and await phenotypic evaluations, and furthermore, permits genetic selection for the particular tolerance allele even when the molecular identity of the actual tolerance QTL is unknown. Tissue samples can be taken, for example, from the endosperm, embryo, or mature/developing plant and screened with the appropriate molecular marker to rapidly determine determined which progeny contain the desired genetics. Linked markers also remove the impact of environmental factors that can often influence phenotypic expression.
[055] Because chromosomal distance is approximately proportional to the frequency of crossing over events between traits, there is an approximate physical distance that correlates with recombination frequency. Marker loci are themselves traits and can be assessed according to standard linkage analysis by tracking the marker loci during segregation. Thus, in the context of the present invention, one cM is equal to a 1 % chance that a marker locus will be separated from another locus (which can be any other trait, e.g. , another marker locus, or another trait locus that encodes a QTL), due to crossing over in a single generation.
[056] When referring to the relationship between two genetic elements, such as a genetic element contributing to tolerance and a proximal marker, "coupling" phase linkage indicates the state where the "favorable" allele at the tolerance locus is physically associated on the same chromosome strand as the "favorable" allele of the respective linked marker locus. In coupling phase, both favorable alleles are inherited together by progeny that inherit that chromosome strand. In "repulsion" phase linkage, the "favorable" allele at the locus of interest (e.g., a QTL for tolerance) is physically linked with an "unfavorable" allele at the proximal marker locus, and the two "favorable" alleles are not inherited together (i.e. , the two loci are "out of phase" with each other).
Quantitative Trait Loci
[057] An allele of a QTL can comprise multiple genes or other genetic factors even within a contiguous genomic region or linkage group, such as a haplotype. As used herein, an allele of a disease tolerance locus can encompass more than one gene or nucleotide sequence where each individual gene or nucleotide sequence is also capable of exhibiting allelic variation and where each gene or nucleotide sequence is also capable of eliciting a phenotypic effect on the quantitative trait in question. In an aspect of the present invention the allele of a QTL comprises one or more genes or nucleic acid sequences that are also capable of exhibiting allelic variation. The use of the term "an allele of a QTL" is thus not intended to exclude a QTL that comprises more than one gene or other genetic factor. Specifically, an "allele of a QTL" in the present in the invention can denote a haplotype within a haplotype window wherein a phenotype can be disease tolerance. A haplotype window is a contiguous genomic region that can be defined, and tracked, with a set of one or more polymorphic markers wherein the polymorphisms indicate identity by descent. A haplotype within that window can be defined by the unique fingerprint of alleles at each marker. As used herein, an allele is one of several alternative forms of a gene occupying a given locus on a chromosome. When all the alleles present at a given locus on a chromosome are the same, that plant is homozygous at that locus. If the alleles present at a given locus on a chromosome differ, that plant is heterozygous at that locus. Plants of the present invention may be homozygous or heterozygous at any particular disease locus or for a particular polymorphic marker.
[058] The principles of QTL analysis and statistical methods for calculating linkage between markers and useful QTL, or between any loci in a genome are well known in the art. Exemplary methods include penalized regression analysis, ridge regression, single point marker analysis, complex pedigree analysis, Bayesian MCMC, , identity-by-descent analysis, interval mapping, composite interval mapping, and Haseman-Elston regression. QTL analyses are often performed with the help of a computer and specialized software available from a variety of public and commercial sources known to those of skill in the art.
Genetic Mapping
[059] A "genetic map" is the relationship of genetic linkage among loci on one or more chromosomes (or linkage groups) within a given species, generally depicted in a diagrammatic or tabular form. "Genetic mapping" is the process of defining the linkage relationships of loci through the use of genetic markers, populations segregating for the markers, and standard genetic principles of recombination frequency. A "genetic map location" is a location on a genetic map relative to surrounding genetic markers on the same linkage group where a specified marker can be found within a given species. In contrast, a physical map of the genome refers to absolute distances (for example, measured in base pairs or isolated and overlapping contiguous genetic fragments, e.g. , contigs). A physical map of the genome does not take into account the genetic behavior (e.g. , recombination frequencies) between different points on the physical map. A "genetic recombination frequency" is the frequency of a crossing over event (recombination) between two genetic loci. Recombination frequency can be observed by following the segregation of markers and/or traits following meiosis. In some cases, two different markers can have the same genetic map coordinates. In that case, the two markers are in such close proximity to each other that recombination occurs between them with such low frequency that it is undetected. [060] Genetic maps are graphical representations of genomes (or a portion of a genome such as a single chromosome) where the distances between markers are measured by the recombination frequencies between them. Plant breeders use genetic maps of molecular markers to increase breeding efficiency through Marker assisted selection (MAS), a process where selection for a trait of interest is not based on the trait itself but rather on the genotype of a marker linked to the trait. A molecular marker that demonstrates reliable linkage with a phenotypic trait provides a useful tool for indirectly selecting the trait in a plant population, especially when accurate phenotyping is difficult, slow, or expensive.
[061] In general, the closer two markers or genomic loci are on the genetic map, the closer they lie to one another on the physical map. A lack of precise proportionality between cM distances and physical distances can exist due to the fact that the likelihood of genetic recombination is not uniform throughout the genome; some chromosome regions are crossover "hot spots," while other regions demonstrate only rare recombination events, if any.
[062] Genetic mapping variability can also be observed between different populations of the same crop species. In spite of this variability in the genetic map that may occur between populations, genetic map and marker information derived from one population generally remains useful across multiple populations in identification of plants with desired traits, counter-selection of plants with undesirable traits and in guiding MAS.
[063] As one of skill in the art will recognize, recombination frequencies (and as a result, genetic map positions) in any particular population are not static. The genetic distances separating two markers (or a marker and a QTL) can vary depending on how the map positions are determined. For example, variables such as the parental mapping populations used, the software used in the marker mapping or QTL mapping, and the parameters input by the user of the mapping software can contribute to the QTL marker genetic map relationships. However, it is not intended that the invention be limited to any particular mapping populations, use of any particular software, or any particular set of software parameters to determine linkage of a particular marker or chromosome interval with the disease tolerance phenotype. It is well within the ability of one of ordinary skill in the art to extrapolate the novel features described herein to any gene pool or population of interest, and using any particular software and software parameters. Indeed, observations regarding genetic markers and chromosome intervals in populations in addition to those described herein are readily made using the teaching of the present disclosure. Association Mapping
[064] Association or LD mapping techniques aim to identify genotype -phenotype associations that are significant. It is effective for fine mapping in outcrossing species where frequent recombination among heterozygotes can result in rapid LD decay. LD is non- random association of alleles in a collection of individuals, reflecting the recombinational history of that region. Thus, LD decay averages can help determine the number of markers necessary for a genome-wide association study to generate a genetic map with a desired level of resolution.
[065] Large populations are better for detecting recombination, while older populations are generally associated with higher levels of polymorphism, both of which contribute to accelerated LD decay. However, smaller effective population sizes tend to show slower LD decay, which can result in more extensive haplotype conservation. Understanding of the relationships between polymorphism and recombination is useful in developing strategies for efficiently extracting information from these resources. Association analyses compare the plants' phenotypic score with the genotypes at the various loci. Subsequently, any suitable maize genetic map (for example, a composite map) can be used to help observe distribution of the identified QTL markers and/or QTL marker clustering using previously determined map locations of the markers.
Marker Assisted Selection
[066] "Introgression" refers to the transmission of a desired allele of a genetic locus from one genetic background to another by. For example, introgression of a desired allele at a specified locus can be transmitted to at least one progeny via a sexual cross between two parents of the same species, where at least one of the parents has the desired allele in its genome. Alternatively, for example, transmission of an allele can occur by recombination between two donor genomes, e.g. , in a fused protoplast, where at least one of the donor protoplasts has the desired allele in its genome. The desired allele can be, e.g. , a selected allele of a marker, a QTL, a transgene, or the like. In any case, offspring comprising the desired allele can be repeatedly backcrossed to a line having a desired genetic background and selected for the desired allele, to result in the allele becoming fixed in a selected genetic background.
[067] A primary motivation for development of molecular markers in crop species is the potential for increased efficiency in plant breeding through marker assisted selection (MAS). Genetic markers are used to identify plants that contain a desired genotype at one or more loci, and that are expected to transfer the desired genotype, along with a desired phenotype to their progeny. Genetic markers can be used to identify plants containing a desired genotype at one locus, or at several unlinked or linked loci (e.g. , a haplotype), and that would be expected to transfer the desired genotype, along with a desired phenotype to their progeny. The present invention provides the means to identify plants that are tolerant, exhibit improved tolerance or are susceptible to ASR infection by identifying plants having a specified allele that is linked to ASR- 1.01.
[068] In general, MAS uses polymorphic markers that have been identified as having a significant likelihood of co-segregation with a tolerance trait. Such markers are presumed to map near a gene or genes that give the plant its tolerance phenotype, and are considered indicators for the desired trait, and are termed QTL markers. Plants are tested for the presence or absence of a desired allele in the QTL marker.
[069] Identification of plants or germplasm that include a marker locus or marker loci linked to a tolerance trait or traits provides a basis for performing marker assisted selection. Plants that comprise favorable markers or favorable alleles are selected for, while plants that comprise markers or alleles that are negatively correlated with tolerance can be selected against. Desired markers and/or alleles can be introgressed into plants having a desired (e.g. , elite or exotic) genetic background to produce an introgressed tolerant plant or germplasm. In some aspects, it is contemplated that a plurality of tolerance markers are sequentially or simultaneous selected and/ or introgressed. The combinations of tolerance markers that are selected for in a single plant is not limited, and can include any combination of markers disclosed herein or any marker linked to the markers disclosed herein, or any markers located within the QTL intervals defined herein.
[070] In some embodiments, the allele that is detected is a favorable allele that positively correlates with disease tolerance or improved disease tolerance. In the case where more than one marker is selected, an allele is selected for each of the markers; thus, two or more alleles are selected. In some embodiments, it can be the case that a marker locus will have more than one advantageous allele, and in that case, either allele can be selected. It will be appreciated that the ability to identify QTL marker loci alleles that correlate with tolerance, improved tolerance or susceptibility of a corn plant to disease conditions provides a method for selecting plants that have favorable marker loci as well. That is, any plant that is identified as comprising a desired marker locus (e.g. , a marker allele that positively correlates with tolerance) can be selected for, while plants that lack the locus, or that have a locus that negatively correlates with tolerance, can be selected against.
[071] In some embodiments, a disease tolerant first corn plant or germplasm (the donor) can be crossed with a second corn plant or germplasm (the recipient, e.g. , an elite or exotic corn, depending on characteristics that are desired in the progeny) to create an introgressed corn plant or germplasm as part of a breeding program designed to improve disease tolerance of the recipient corn plant or germplasm. In some aspects, the recipient plant can also contain one or more disease tolerant loci, which can be qualitative or quantitative trait loci. In another aspect, the recipient plant can contain a transgene.
[072] In some embodiments, the recipient corn plant or germplasm will typically display reduced tolerance to disease conditions as compared to the first corn plant or germplasm, while the introgressed corn plant or germplasm will display an increased tolerance to disease conditions as compared to the second plant or germplasm. An introgressed corn plant or germplasm produced by these methods are also a feature of this invention.
[073] MAS is a powerful shortcut to selecting for desired phenotypes and for introgressing desired traits into cultivars (e.g. , introgressing desired traits into elite lines). MAS is easily adapted to high throughput molecular analysis methods that can quickly screen large numbers of plant or germplasm genetic material for the markers of interest and is much more cost effective than raising and observing plants for visible traits.
[074] When a population is segregating for multiple loci affecting one or multiple traits, e.g. , multiple loci involved in tolerance, or multiple loci each involved in tolerance or tolerance to different diseases, the efficiency of MAS compared to phenotypic screening becomes even greater, because all of the loci can be evaluated in the lab together from a single sample of DNA.
Marker Assisted Backcrossing
[075] One application of MAS, is to use the tolerance or improved tolerance markers to increase the efficiency of an introgression effort aimed at introducing a tolerance QTL into a desired (typically high yielding) background. If the nucleic acids from a plant are positive for a desired genetic marker allele, the plant can be self fertilized to create a true breeding line with the same genotype, or it can be crossed with a plant with the same marker or with other characteristics to create a sexually crossed hybrid generation. [076] Another use of MAS in plant breeding is to assist the recovery of the recurrent parent genotype by backcross breeding. Backcross breeding is the process of crossing a progeny back to one of its parents or parent lines. Backcrossing is usually done for the purpose of introgressing one or a few loci from a donor parent (e.g. , a parent comprising desirable tolerance marker loci) into an otherwise desirable genetic background from the recurrent parent (e.g. , an otherwise high yielding line). The more cycles of back crossing that are done, the greater the genetic contribution of the recurrent parent to the resulting introgressed variety. This is often necessary, because tolerant plants may be otherwise undesirable, e.g. , due to low yield, low fecundity, or the like. In contrast, strains which are the result of intensive breeding programs may have excellent yield, fecundity or the like, merely being deficient in one desired trait such as tolerance to ASR infection.
[077] Moreover, in another aspect, while maintaining the introduced markers associated with tolerance, the genetic contribution of the plant providing disease tolerance can be reduced by back-crossing or other suitable approaches. In one aspect, the nuclear genetic material derived from the donor material in the plant can be less than or about 50%, less than or about 25%, less than or about 13%, less than or about 5%, 3%, 2% or 1%, but that the recipient remains resistant to disease.
[078] Genetic diversity is important for long term genetic gain in any breeding program. With limited diversity, genetic gain will eventually plateau when all of the favorable alleles have been fixed within the elite population. One objective is to incorporate diversity into an elite pool without losing the genetic gain that has already been made and with the minimum possible investment. MAS provide an indication of which genomic regions and which favorable alleles from the original ancestors have been selected for and conserved over time, facilitating efforts to incorporate favorable variation from exotic germplasm sources (parents that are unrelated to the elite gene pool) in the hopes of finding favorable alleles that do not currently exist in the elite gene pool.
[079] Systems, including automated systems for selecting plants that comprise a marker of interest and/or for correlating presence of the marker with tolerance are also a feature of the invention. These systems can include probes relevant to marker locus detection, detectors for detecting labels on the probes, appropriate fluid handling elements and temperature controllers that mix probes and templates and/or amplify templates and systems instructions that correlate label detection to the presence of a particular marker locus or allele. [080] In an aspect, this invention could be used on any plant. In another aspect, the plant is selected from the genus Zea. In another aspect, the plant is selected from the species Zea mays. In a further aspect, the plant is selected from the subspecies Zea mays L. ssp. mays. In an additional aspect, the plant is selected from the group Zea mays L. subsp. mays Indentata, otherwise known as dent corn. In another aspect, the plant is selected from the group Zea mays L. subsp. mays Indurata, otherwise known as flint corn. In an aspect, the plant is selected from the group Zea mays L. subsp. mays Saccharata, otherwise known as sweet corn. In another aspect, the plant is selected from the group Zea mays L. subsp. mays Amylacea, otherwise known as flour corn. In a further aspect, the plant is selected from the group Zea mays L. subsp. mays Everta, otherwise known as pop corn. Zea plants include hybrids, inbreds, partial inbreds, or members of defined or undefined populations.
[081] In a one aspect, the present invention provides a plant to be assayed for tolerance or susceptibility to disease by any method to determine whether a plant is resistant, susceptible, or whether it exhibits some degree of tolerance or susceptibility. Populations of plants can be similarly characterized in this manner, or further characterized as segregating for the trait of disease tolerance.
[082] It is further understood that a plant of the present invention may exhibit the characteristics of any relative maturity group. In an aspect, the maturity group is selected from the group consisting of early maturing varieties, mid season maturing varieties, and full season varieties.
[083] In another aspect, corn seed of the invention can be subjected to various treatments. For example, the seeds can be treated to improve germination by priming the seeds or by disinfection to protect against seed-born pathogens. In another aspect, seeds can be coated with any available coating to improve, for example, plantability, seed emergence, and protection against seed-born pathogens. Seed coating can be any form of seed coating including, but not limited to, pelleting, film coating, and encrustments.
[084] It is further understood, that the present invention provides bacterial, viral, microbial, insect, mammalian and plant cells comprising the nucleic acid molecules of the present invention.
[085] In another aspect, a corn plant of the invention can show a comparative tolerance compared to a non-tolerant control corn plant. In this aspect, a control corn plant will preferably be genetically similar except for the disease tolerance allele or alleles in question. Such plants can be grown under similar conditions with equivalent or near equivalent exposure to the pathogen.
Definitions
[086] Descriptions of commonly used breeding terms and methods for crossing and producing hybrids that are used to describe present invention can be found in one of several reference books (Allard, "Principles of Plant Breeding," John Wiley & Sons, NY, U. of CA, Davis, CA, 50-98, 1960; Simmonds, "Principles of crop improvement," Longman, Inc., NY, 369-399, 1979; Sneep and Hendriksen, "Plant breeding perspectives," Wageningen (ed), Center for Agricultural Publishing and Documentation, 1979; Fehr, In: Soybeans: Improvement, Production and Uses, 2nd Edition, Monograph., 16:249, 1987; Fehr, "Principles of variety development," Theory and Technique, (Vol. 1) and Crop Species Soybean (Vol. 2), Iowa State Univ., Macmillan Pub. Co., NY, 360-376, 1987).
[087] The definitions and methods provided define the present invention and guide those of ordinary skill in the art in the practice of the present invention. Unless otherwise noted, terms are to be understood according to conventional usage by those of ordinary skill in the relevant art. Examples of resources describing many of the terms related to molecular biology used herein can be found in in Alberts et ah, Molecular Biology of The Cell, 5* Edition, Garland Science Publishing, Inc.: New York, 2007; Rieger et ah , Glossary of Genetics: Classical and Molecular, 5th edition, Springer- Verlag: New York, 1991 ; King et al, A Dictionary of Genetics, 6th ed, Oxford University Press: New York, 2002; and Lewin, Genes Icorn, Oxford University Press: New York, 2007. The nomenclature for DNA bases as set forth at 37 CFR § 1.822 is used.
[088] Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.
[089] "Adjacent", when used to describe a nucleic acid molecule that hybridizes to
DNA containing a polymorphism, refers to a nucleic acid that hybridizes to DNA sequences that directly abut the polymorphic nucleotide base position. For example, a nucleic acid molecule that can be used in a single base extension assay is "adjacent" to the polymorphism. [090] "Allele" refers to an alternative nucleic acid sequence at a particular locus; the length of an allele can be as small as 1 nucleotide base, but is typically larger. For example, a first allele can occur on one chromosome, while a second allele occurs on a second homologous chromosome, e.g. , as occurs for different chromosomes of a heterozygous individual, or between different homozygous or heterozygous individuals in a population. A favorable allele is the allele at a particular locus that confers, or contributes to, an agronomically desirable phenotype, or alternatively, is an allele that allows the identification of susceptible plants that can be removed from a breeding program or planting. A favorable allele of a marker is a marker allele that segregates with the favorable phenotype, or alternatively, segregates with susceptible plant phenotype, therefore providing the benefit of identifying disease prone plants. A favorable allelic form of a chromosome interval is a chromosome interval that includes a nucleotide sequence that contributes to superior agronomic performance at one or more genetic loci physically located on the chromosome interval. "Allele frequency" refers to the frequency (proportion or percentage) at which an allele is present at a locus within an individual, within a line, or within a population of lines. For example, for an allele "A," diploid individuals of genotype "AA," "Aa," or "aa" have allele frequencies of 1.0, 0.5, or 0.0, respectively. One can estimate the allele frequency within a line by averaging the allele frequencies of a sample of individuals from that line. Similarly, one can calculate the allele frequency within a population of lines by averaging the allele frequencies of lines that make up the population. For a population with a finite number of individuals or lines, an allele frequency can be expressed as a count of individuals or lines (or any other specified grouping) containing the allele. An allele positively correlates with a trait when it is linked to it and when presence of the allele is an indictor that the desired trait or trait form will occur in a plant comprising the allele. An allele negatively correlates with a trait when it is linked to it and when presence of the allele is an indicator that a desired trait or trait form will not occur in a plant comprising the allele.
[091] "Crossed" or "cross" means to produce progeny via fertilization (e.g. cells, seeds or plants) and includes crosses between plants (sexual) and self fertilization (selfing).
[092] "Elite line" means any line that has resulted from breeding and selection for superior agronomic performance. Numerous elite lines are available and known to those of skill in the art of corn breeding. An "elite population" is an assortment of elite individuals or lines that can be used to represent the state of the art in terms of agronomically superior genotypes of a given crop species, such as corn. Similarly, an "elite germplasm" or elite strain of germplasm is an agronomically superior germplasm, typically derived from and/or capable of giving rise to a
[093] "Exogenous nucleic acid" is a nucleic acid that is not native to a specified system (e.g. , a germplasm, plant, variety, etc.), with respect to sequence, genomic position, or both. As used herein, the terms "exogenous" or "heterologous" as applied to polynucleotides or polypeptides typically refers to molecules that have been artificially supplied to a biological system (e.g. , a plant cell, a plant gene, a particular plant species or variety or a plant chromosome under study) and are not native to that particular biological system. The terms can indicate that the relevant material originated from a source other than a naturally occurring source, or can refer to molecules having a non-natural configuration, genetic location or arrangement of parts. In contrast, for example, a "native" or "endogenous" gene is a gene that does not contain nucleic acid elements encoded by sources other than the chromosome or other genetic element on which it is normally found in nature. An endogenous gene, transcript or polypeptide is encoded by its natural chromosomal locus, and not artificially supplied to the cell.
[094] "Genetic element" or "gene" refers to a heritable sequence of DNA, i.e. , a genomic sequence, with functional significance. The term "gene" can also be used to refer to, e.g. , a cDNA and/or a mRNA encoded by a genomic sequence, as well as to that genomic sequence.
[095] "Genotype" is the genetic constitution of an individual (or group of individuals) at one or more genetic loci, as contrasted with the observable trait (the phenotype). Genotype is defined by the allele(s) of one or more known loci that the individual has inherited from its parents. The term genotype can be used to refer to an individual's genetic constitution at a single locus, at multiple loci, or, more generally, the term genotype can be used to refer to an individual's genetic make-up for all the genes in its genome. A "haplotype" is the genotype of an individual at a plurality of genetic loci. Typically, the genetic loci described by a haplotype are physically and genetically linked, i. e. , on the same chromosome interval. The terms "phenotype," or "phenotypic trait" or "trait" refers to one or more trait of an organism. The phenotype can be observable to the naked eye, or by any other means of evaluation known in the art, e.g., microscopy, biochemical analysis, genomic analysis, an assay for a particular disease tolerance, etc. In some cases, a phenotype is directly controlled by a single gene or genetic locus, i.e. , a "single gene trait." In other cases, a phenotype is the result of several genes. [096] "Germplasm" refers to genetic material of or from an individual (e.g. , a plant), a group of individuals (e.g. , a plant line, variety or family), or a clone derived from a line, variety, species, or culture. The germplasm can be part of an organism or cell, or can be separate from the organism or cell. In general, germplasm provides genetic material with a specific molecular makeup that provides a physical foundation for some or all of the hereditary qualities of an organism or cell culture. As used herein, germplasm includes cells, seed or tissues from which new plants may be grown, or plant parts, such as leafs, stems, pollen, or cells that can be cultured into a whole plant.
[097] "Linkage disequilibrium" refers to a non-random segregation of genetic loci or traits (or both). In either case, linkage disequilibrium implies that the relevant loci are within sufficient physical proximity along a length of a chromosome so that they segregate together with greater than random (i.e. , non-random) frequency (in the case of co-segregating traits, the loci that underlie the traits are in sufficient proximity to each other). Linked loci co- segregate more than 50% of the time, e.g. , from about 51% to about 100% of the time. The tern "physically linked" is sometimes used to indicate that two loci, e.g. , two marker loci, are physically present on the same chromosome. Advantageously, the two linked loci are located in close proximity such that recombination between homologous chromosome pairs does not occur between the two loci during meiosis with high frequency, e.g. , such that linked loci cosegregate at least about 90% of the time, e.g., 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.75%, or more of the time.
[098] "Locus" a chromosome region where a polymorphic nucleic acid, trait determinant, gene or marker is located. The loci of this invention comprise one or more polymorphisms in a population; i.e. , alternative alleles are present in some individuals. A "gene locus" is a specific chromosome location in the genome of a species where a specific gene can be found.
[099] "Marker Assay" means a method for detecting a polymorphism at a particular locus using a particular method, e.g. measurement of at least one phenotype (such as seed color, flower color, or other visually detectable trait), restriction fragment length polymorphism (RFLP), single base extension, electrophoresis, sequence alignment, allelic specific oligonucleotide hybridization (ASO), random amplified polymorphic DNA (RAPD), microarray-based technologies, and nucleic acid sequencing technologies, etc. "Marker Assisted Selection" (MAS) is a process by which phenotypes are selected based on marker genotypes. [0100] "Molecular phenotype" is a phenotype detectable at the level of a population of one or more molecules. Such molecules can be nucleic acids, proteins, or metabolites. A molecular phenotype could be an expression profile for one or more gene products, e.g. , at a specific stage of plant development, in response to an environmental condition or stress, etc.
[0101] "Operably linked" refers to the association of two or more nucleic acid elements in a recombinant DNA construct, e.g. as when a promoter is operably linked with DNA that is transcribed to RNA whether for expressing or suppressing a protein. Recombinant DNA constructs can be designed to express a protein which can be an endogenous protein, an exogenous homologue of an endogenous protein or an exogenous protein with no native homologue. Alternatively, recombinant DNA constructs can be designed to suppress the level of an endogenous protein, e.g. by suppression of the native gene. Such gene suppression can be effectively employed through a native RNA interference (RNAi) mechanism in which recombinant DNA comprises both sense and anti-sense oriented DNA matched to the gene targeted for suppression where the recombinant DNA is transcribed into RNA that can form a double-strand to initiate an RNAi mechanism. Gene suppression can also be effected by recombinant DNA that comprises anti-sense oriented DNA matched to the gene targeted for suppression. Gene suppression can also be effected by recombinant DNA that comprises DNA that is transcribed to a microRNA matched to the gene targeted for suppression.
[0102] "Percent identity" or " identity" means the extent to which two optimally aligned DNA or protein segments are invariant throughout a window of alignment of components, for example nucleotide sequence or amino acid sequence. An "identity fraction" for aligned segments of a test sequence and a reference sequence is the number of identical components that are shared by sequences of the two aligned segments divided by the total number of sequence components in the reference segment over a window of alignment which is the smaller of the full test sequence or the full reference sequence.
[0103] "Phenotype" means the detectable characteristics of a cell or organism which can be influenced by genotype.
[0104] "Plant" refers to a whole plant any part thereof, or a cell or tissue culture derived from a plant, comprising any of: whole plants, plant components or organs (e.g. , leaves, stems, roots, etc.), plant tissues, seeds, plant cells, and/or progeny of the same. A plant cell is a biological cell of a plant, taken from a plant or derived through culture from a cell taken from a plant. [0105] "Polymorphism" means the presence of one or more variations in a population. A polymorphism may manifest as a variation in the nucleotide sequence of a nucleic acid or as a variation in the amino acid sequence of a protein. Polymorphisms include the presence of one or more variations of a nucleic acid sequence or nucleic acid feature at one or more loci in a population of one or more individuals. The variation may comprise but is not limited to one or more nucleotide base changes, the insertion of one or more nucleotides or the deletion of one or more nucleotides. A polymorphism may arise from random processes in nucleic acid replication, through mutagenesis, as a result of mobile genomic elements, from copy number variation and during the process of meiosis, such as unequal crossing over, genome duplication and chromosome breaks and fusions. The variation can be commonly found or may exist at low frequency within a population, the former having greater utility in general plant breeding and the latter may be associated with rare but important phenotypic variation. Useful polymorphisms may include single nucleotide polymorphisms (SNPs), insertions or deletions in DNA sequence (Indels), simple sequence repeats of DNA sequence (SSRs), a restriction fragment length polymorphism, and a tag SNP. A genetic marker, a gene, a DNA-derived sequence, a RNA-derived sequence, a promoter, a 5' untranslated region of a gene, a 3' untranslated region of a gene, microRNA, siRNA, a tolerance locus, a satellite marker, a transgene, mRNA, ds mRNA, a transcriptional profile, and a methylation pattern may also comprise polymorphisms. In addition, the presence, absence, or variation in copy number of the preceding may comprise polymorphisms.
[0106] A "population of plants" or "plant population" means a set comprising any number, including one, of individuals, objects, or data from which samples are taken for evaluation, e.g. estimating QTL effects. Most commonly, the terms relate to a breeding population of plants from which members are selected and crossed to produce progeny in a breeding program. A population of plants can include the progeny of a single breeding cross or a plurality of breeding crosses, and can be either actual plants or plant derived material, or in silico representations of the plants. The population members need not be identical to the population members selected for use in subsequent cycles of analyses or those ultimately selected to obtain final progeny plants. Often, a plant population is derived from a single biparental cross, but may also derive from two or more crosses between the same or different parents. Although a population of plants may comprise any number of individuals, those of skill in the art will recognize that plant breeders commonly use population sizes ranging from one or two hundred individuals to several thousand, and that the highest performing 5-20% of a population is what is commonly selected to be used in subsequent crosses in order to improve the performance of subsequent generations of the population.
[0107] "Resistance locus" means a locus associated with resistance to disease. For instance, a resistance locus according to the present invention may, in one embodiment, control resistance or susceptibility for one or more races of Colletotrichum graminicola.
[0108] "Resistance allele" means the nucleic acid sequence associated with resistance to disease.
[0109] "Recombinant" in reference to a nucleic acid or polypeptide indicates that the material {e.g. , a recombinant nucleic acid, gene, polynucleotide, polypeptide, etc.) has been altered by human intervention. The term recombinant can also refer to an organism that harbors recombinant material, e.g. , a plant that comprises a recombinant nucleic acid is considered a recombinant plant.
[0110] "Tolerance" or "improved tolerance" in a plant to disease conditions is an indication that the plant is less affected by disease conditions with respect to yield, survivability and/or other relevant agronomic measures, compared to a less tolerant, more "susceptible" plant. Tolerance is a relative term, indicating that a "tolerant" plant survives and/or produces better yields in disease conditions compared to a different (less tolerant) plant {e.g. , a different corn line strain) grown in similar disease conditions. As used in the art, disease "tolerance" is sometimes used interchangeably with disease "resistance." One of skill will appreciate that plant tolerance to disease conditions varies widely, and can represent a spectrum of more-tolerant or less-tolerant phenotypes. However, by simple observation, one of skill can generally determine the relative tolerance or susceptibility of different plants, plant lines or plant families under disease conditions, and furthermore, will also recognize the phenotypic gradations of "tolerant."
[0111] "Transgenic plant" refers to a plant that comprises within its cells a heterologous polynucleotide. Generally, the heterologous polynucleotide is stably integrated within the genome such that the polynucleotide is passed on to successive generations. The heterologous polynucleotide may be integrated into the genome alone or as part of a recombinant expression cassette. "Transgenic" is used herein to refer to any cell, cell line, callus, tissue, plant part or plant, the genotype of which has been altered by the presence of heterologous nucleic acid including those transgenic organisms or cells initially so altered, as well as those created by crosses or asexual propagation from the initial transgenic organism or cell. The term "transgenic" as used herein does not encompass the alteration of the genome (chromosomal or extrachromosomal) by conventional plant breeding methods (e.g. , crosses) or by naturally occurring events such as random cross-fertilization, non-recombinant viral infection, non-recombinant bacterial transformation, non-recombinant transposition, or spontaneous mutation.
[0112] "Vector" is a polynucleotide or other molecule that transfers nucleic acids between cells. Vectors are often derived from plasmids, bacteriophages, or viruses and optionally comprise parts which mediate vector maintenance and enable its intended use. A "cloning vector" or "shuttle vector" or "sub cloning vector" contains operably linked parts that facilitate subcloning steps (e.g. , a multiple cloning site containing multiple restriction endonuclease sites). The term "expression vector" as used herein refers to a vector comprising operably linked polynucleotide sequences that facilitate expression of a coding sequence in a particular host organism (e.g. , a bacterial expression vector or a plant expression vector).
[0113] "Yield" is the culmination of all agronomic traits as determined by the productivity per unit area of a particular plant product of commercial value. "Agronomic traits," include the underlying genetic elements of a given plant variety that contribute to yield over the course of growing season.
[0114] As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
EXAMPLES
Example 1. Inoculation and assessment of ASR tolerance phenotypes.
[0115] Corn plants grown in a field in Brazil were inoculated 14 days after the mid- silk stage, i.e. the point when 50% of the plants within a given row had reached the Rl (silking) growth stage, by injecting 5xl05 Colletotrichum graminicola spores suspended in lmL of distilled water. Thirty days after inoculation, the severity of Anthracnose stalk rot in 2000 plants was visually assessed by splitting each stalk longitudinally to expose the pith. Each pith was examined to determine 1) the total number of internodes that displayed visual legions characteristic of the disease, and 2) the total number of internodes wherein visual legions had infected >75 of the tissue within the internode, as summarized in Table 2. These two numbers were then summed into a disease score phenotype for each plant, with scores of 10 converted to 9 to fit a scale ranging from 1 (highly resistant) to 9 (highly susceptible). The individual plant scores of each row were then averaged and the average was reported as a final score for the row.
Table 2 . Rating Scale of relative ASR infection tolerance phenotypes.
Figure imgf000036_0001
Example 2. Assays useful for detecting ASR tolerance genotypes.
[0116] For convenience, primer sequences for amplifying exemplary SNP marker loci linked to the ASR-1.01 QTL and the probes used to genotype the corresponding SNP sequences are provided in Table 3. Primer and probe synthesis is within the skill of the art once the SNP position in the corn genome is provided. One of skill in the art will also immediately recognize that other sequences to either side of the given primers can be used in place of the given primers, so long as the primers can amplify a region that includes the allele to be detected. Further, it will be appreciated that the precise probe to be used for detection can vary, e.g. , any probe that can identify the region of a marker amplicon to be detected can be substituted for those examples provided herein. Also, configuration of the amplification primers and detection probes can, of course, vary. Thus, the invention is not limited to the primers, probes, or marker sequences specifically recited herein. Table 3. Primers and probes useful for detecting ASR tolerance SNPs.
Figure imgf000037_0001
[0117] Illustrative ASR tolerance marker DNA sequences SEQ ID NOs:l, 10, or 15 can be amplified using the primers indicated in Table 3 using SEQ ID NOs:18 and 35, 27 and 44, or 32 and 49, respectively, and detected with probes indicated in Table 3 as SEQ ID NOs:52 and 69, 61 and 78, or 66 and 83, respectively.
Example 2. Marker-Trait Association Study
[0118] 192 doubled-haploid plants derived from the cross of a resistant maize inbred line and a susceptible female maize inbred line were phenotyped for ASR tolerance in two field replicates at a research site in Brazil using methods described in the art and the rating scale in Example 1. These 192 plants were then genotyped using 300 SNPs that collectively spanned each chromosome in the maize genome. Loci were eliminated from further analysis in where they were monomorphic in the subject population studied.
[0119] Marker-trait association studies were performed using both single-marker analysis (SMA) and composite interval mapping (CIM). For each marker, the thresholds of Likelihood ratio between full and null models for CIM were based on 1000 permutation tests and the thresholds (p-value) for SMA were based on 10,000 permutation tests (Churchill and Doerge 1994).
[0120] Table 4 lists the effect estimates on ASR tolerance phenotype ratings associated with each marker (SEQ ID NO). Each row provides the SEQ ID NO of the marker, and the estimated effect that the marker polymorphism had on the ASR phenotype. The statistical significance (p-value) of the association between the marker and the ASR tolerance rating in each case was p-val < 0.001.
Table 4. Statistical associations of markers associated with ASR-1.01 on maize chromosome 1.
Figure imgf000038_0001
*P-value is based on 10,000 permutation
tests
[0121] For example, SEQ ID NO:3 was associated with a 0.519 change in ASR tolerance rating by one copy of the favorable allele. SEQ ID NO:5 was associated with a 0.437 change in ASR tolerance rating by one copy of the favorable allele. ASR tolerance ratings were generated using the methods described in Example 1.
[0122] Table 5 describes the profile of the ASR-1.01 QTL revealed by the CIM analysis, including the chromosome interval where the Likelihood ratio was within the threshold of p-value < 0.01. Table 5. Results of the composite interval mapping (CIM) analysis. Markers umc2228 and haclOlb are the closest markers t to the points on chromosome 1 where the CIM Likelihood ratio remained within the threshold of p- value < 0.01. The peak of the Likelihood ratio corresponds to the ASR- 1.01 locus.
Figure imgf000039_0001
[0123] Thus, the CIM analysis revealed that markers within the interval flanked by and including markers umc2228 and haclOlb were highly associated with ASR tolerance (p- value < 0.01). Markers bordering this region also find utility with this invention, but their associations with ASR tolerance tend to decrease as their locations become further removed from ASR-1.01.
Example 3. Detecting ASR tolerance in a population of plants and monitoring the introgression of ASR tolerance loci from one plant line into another via MAS.
[0124] A population of corn plants can be phenotyped using any method that gauges the effect of ASR infection on a plant trait, including the methods described herein. The genotypes of the plants in the population at one or more markers that map to the chromosome intervals associated with ASR tolerance, or at one or more markers closely linked to one of those intervals, can also be determined. In one embodiment, statistical associations can then be made between the recorded phenotypes and the genotypes using a variety of methods known in the art, including those described herein.
[0125] In one embodiment, genotypes of offspring derived from one or more individuals in the population can be compared to the genotypes of the parents at one or more marker loci linked to the ASR-1.01 genotypes of the parents at those same loci. Individuals that share marker genotypes with the resistant parent at one or more markers can then be selected for advancement in the breeding program. Individuals that do not share marker genotypes with the resistant parent, or individuals that do share marker genotypes with the susceptible parent, can be discarded. This process saves the laborious and time consuming process of phenotyping plants to verify which are resistant or susceptible.
[0126] In some embodiments, useful markers comprise any marker that is within or genetically linked to the ASR-1.01 QTL. In other embodiments, useful markers comprise any marker that is within between publically available markers TIDP 7054 and AY104360. In other embodiments, associations are made between genotypes for one or more SNP markers that map between publically available markers TIDP 7054 and AY104360.
[0127] Selections and assays may be performed on single loci, or simultaneously on multiple loci. For example, a breeder skilled in the art could base advancement decisions on the genotypes of markers linked to ASR- 1.101 and genotypes of markers linked to other loci, simultaneously. For instance, a breeder may require that the same plant must exhibit genotypes at one or more markers linked to ASR-1.01 and/or at one or more markers linked to any other locus in order to be advanced. In other embodiments, a single genotype at only one locus may be sufficient for advancement.
[0128] By selecting only those individuals with the desired genotype for advancement in the breeding program, the frequency of desired alleles and desired phenotypes can be artificially increased in future generations.
[0129] The introgression of one or more desired loci from a donor line into another is achieved via repeated backcrossing to a recurrent parent accompanied by selection to retain one or more ASR tolerance loci from the donor parent. Markers associated with ASR tolerance are assayed in progeny and those progeny with one or more ASR tolerance markers are selected for advancement. In another aspect, one or more markers can be assayed in the progeny to select for plants with the genotype of the agronomically elite parent. This invention anticipates that trait introgression activities will require more than one generation, wherein progeny are crossed to the recurrent (agronomically elite) parent or selfed. Selections are made based on the presence of one or more ASR tolerance markers and can also be made based on the recurrent parent genotype, wherein screening is performed on a genetic marker and/or phenotype basis. In another embodiment, markers of this invention can be used in conjunction with other markers, ideally at least one on each chromosome of the corn genome, to track the introgression of ASR tolerance loci into elite germplasm. In yet another embodiment, at least 100 SNP markers assorted across the 10 chromosomes of corn will be useful in conjunction with the SNP molecular markers of the present invention to follow the introgression of ASR tolerance into elite germplasm. In a still another embodiment, about three hundred fifty SNP markers, distributed every 5 centimorgans across the 10 chromosomes of the corn genetic linkage map, will be useful in conjunction with the SNP molecular markers of the present invention to follow the introgression of ASR tolerance into elite germplasm. In another embodiment, QTLs associated with ASR tolerance will be useful in conjunction with SNP molecular markers of the present invention to combine quantitative and qualitative ASR tolerance in the same plant. It is within the scope of this invention to utilize the methods and compositions for trait integration of ASR tolerance. It is contemplated by the inventors that the present invention will be useful for developing commercial varieties with ASR tolerance and an agronomically elite phenotype.
[0130] For example, one skilled in the art can use one or more markers linked to
ASR-1.01, for example, those listed in Table 1, to select plants for ASR tolerance genotypes arising from the donor while selecting for the recipient genotypes in adjacent chromosome regions. In practice, this reduces the amount of linkage drag from the donor genome that maybe associated with undesirable agronomic properties. This backcrossing procedure is implemented at any stage in line development and occurs in conjunction with breeding for superior agronomic characteristics or one or more traits of interest, including transgenic and nontransgenic traits.
[0131] Alternatively, a forward breeding approach is employed wherein one or more
ASR tolerance loci can be monitored for successful introgression following a cross with a susceptible parent with subsequent generations genotyped for one or more ASR tolerance loci and for one or more additional traits of interest, including transgenic and nontransgenic traits.
[0132] This invention can be used on populations other than those specifically described in this application without altering the methods described herein. Although different parents may have different genotypes at different markers, the method of using this invention is fundamentally identical. Parents are first phenotyped for ASR tolerance, genotyped at each marker, and then those genotypes are used to infer resistant or susceptible phenotypes in progeny derived from those parents, or in any other population where the genotypes are associated with the same phenotypes.
[0133] All patent and non-patent documents cited in this specification are incorporated herein by reference in their entireties, to the same extent as if each individual was specifically and individually indicated to be incorporated by reference. Documents cited herein as being available from the World Wide Web at certain internet addresses are also incorporated herein by reference in their entireties. Certain biological sequences referenced herein by their "NCBI Accession Number" can be accessed through the National Center of Biotechnology Information.
[0134] It is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Modifications in arrangement and detail that do not depart from the principles of the invention described herein are considered to fall within the spirit and scope of the appended claims. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.

Claims

Claim 1. A method of obtaining a corn plant with enhanced anthracnose stalk rot tolerance comprising:
a) providing a population of corn plants;
b) detecting the presence of a genetic marker that is genetically linked to an anthracnose stalk rot tolerance locus located between markers TIDP7054 and AY104360 in the population;
c) selecting from the population at least a first plant containing said genetic marker.
Claim 2. The method of claim 1 , further defined as comprising selecting at least two plants from said population, thereby forming a population of corn plants with said genetic marker and enhanced anthracnose stalk rot tolerance.
Claim 3. The method of claim 1, wherein the plant containing the genetic marker comprises said markers TIDP7054 and AY104360.
Claim 4. The method of claim 1, wherein the anthracnose stalk rot tolerance locus was introgressed into said population of corn plants from a starting plant or population of corn plants containing said locus.
Claim 5. The method of claim 1, wherein the genetic marker is selected from the group consisting of TIDP7054, umc2124a, les22, IDP1489, TIDP6496, dupssr26, umc2228, IDP4988, IDP252, IDP9114, IDP9114, SEQ ID NO:l, bnlg2295, IMR18, TIDP8768, gpm305, SEQ ID NO:2, TIDP7103, IDP5866, SEQ ID NO:3, IDP4792, SEQ ID NO:4, TIDP7049, SEQ ID NO:5, TIDP4596, SEQ ID NO:6, TIDP9243, umcl515, umc2230, SEQ ID NO:7, SEQ ID NO:8, TIDP5625, pco076392, umcl469, SEQ ID NO:9, TIDP8792, SEQ ID NO:10, IDP1407, SEQ ID NO:ll, IDP8606, SEQ ID NO:12, SEQ ID NO:13, IDP4814, SEQ ID NO:14, umc2231, SEQ ID NO:15, IDP6975, SEQ ID NO:16, AI855190, CG694169, IDP637, IDP34, SEQ ID NO: 17, bif2, uaz276, haclOlb, umcl988, IDP451, umcll23, npi429, umcl398, and AY104360.
Claim 6. The method of claim 1, wherein the genetic marker is genetically linked to an anthracnose stalk rot tolerance locus located between markers umc2228 and IDP451.
Claim 7. The method of claim 1 wherein the genetic marker is genetically linked to an anthracnose stalk rot tolerance locus located between markers umc2228 and haclOlb.
Claim 8. The method of claim 1 wherein the genetic marker is genetically linked to an anthracnose stalk rot tolerance locus located between markers SEQ ID NO: 2 and IDP637.
Claim 9 The method of claim 1 wherein the genetic marker is genetically linked to an anthracnose stalk rot tolerance locus located between markers umcl515 and IDP1407.
Claim 10. A method of selecting an anthracnose stalk rot (ASR) tolerant plant comprising genotyping a plurality of plants for a marker associated with ASR tolerance, wherein said marker is located within a locus defined as flanked by markers TIDP7054 and AY104360, and selecting a plant comprising said marker that is ASR tolerant.
Claim 11. The method of claim 10, further comprising producing a progeny plant with ASR tolerance from said ASR tolerant plant.
Claim 12. The method of claim 11, wherein producing the progeny plant comprises marker assisted selection for the ASR tolerance.
Claim 13. The method of claim 11, wherein the progeny plant is an F2-F6 progeny plant.
Claim 14. The method of claim 11, wherein producing the progeny plant comprises backrossing.
Claim 15. A method of creating a population of corn plants comprising at least one allele associated with anthracnose stalk rot tolerance comprising at least one sequence selected from the group consisting of SEQ ID NOs: 1 - 17, the method comprising the steps of:
a) genotyping a first population of corn plants, said population containing at least one allele associated with anthracnose stalk rot tolerance, the at least one allele associated with anthracnose stalk rot tolerance comprising at least one sequence selected from the group consisting of SEQ ID NOs: 1 - 17;
b) selecting from said first population one or more corn plants containing said at least one allele associated with anthracnose stalk rot tolerance comprising at least one sequence selected from the group consisting of SEQ ID NOs: 1 - 17; and c) producing from said selected corn plants a second population, thereby creating a population of corn plants comprising at least one allele associated with anthracnose stalk rot tolerance comprising at least one sequence selected from the group consisting of SEQ ID NOs: 1 - 17.
PCT/US2014/027702 2013-03-15 2014-03-14 Methods of creating fungi tolerant corn plants and compositions thereof WO2014152759A2 (en)

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