WO2012065629A1

WO2012065629A1 - Resistance to nasonovia ribisnigri biotype 1 (nr:1) from lactuca serriola

Info

Publication number: WO2012065629A1
Application number: PCT/EP2010/067589
Authority: WO
Inventors: Arnaud Paul Pierre Thabuis; Korstiaan Cornelis Teekens; Zeger Otto Van Herwijnen
Original assignee: Rijk Zwaan Zaadteelt En Zaadhandel B.V.
Priority date: 2010-11-16
Filing date: 2010-11-16
Publication date: 2012-05-24
Also published as: AU2011331262A1; JP2013544093A; CA2814325A1; WO2012066008A1; US20130239250A1; AU2011331262B2

Abstract

The present invention relates to a lettuce plant (Lactuca sativa L.) resistant against Nasonovia ribisingi biotype 1 (Nr : 1) representative seeds of which were deposited under NCIMB accession number 41763. Such lettuce plant is obtainable by crossing a lettuce plant with a plant grown from seeds of seedlot 10G.913569 representative seeds of which were deposited with the NCIMB under NCIMB accession number 41763 and selecting preferably in the F2 progeny of the cross for plants being resistant against Nasonovia ribisingi biotype 1 (Nr: 1).

Description

RESISTANCE TO NASONOVIA RIBISNIGRI BIOTYPE 1 (NR : 1 ) FROM

LACTUCA SERRIOLA

Field of the invention

The present invention relates to lettuce (Lactuca sativa L.) plants being resistant against the lettuce aphid Nasonovia ribisnigri (Mosley) . The invention further relates to parts of the plants, in particular to the seeds and to other propagation material, and to progeny of the plants.

Background

The lettuce aphid (Nasonovia ribisnigri (Mosley) is a major pest occurring in lettuce worldwide. The problem started to be severe for lettuce production in the 70s in North Western Europe and spread rapidly all across Europe. In the 80s, the aphid was detected in Canada. Later on, the problem was reported in the USA (California and Arizona) . More recently, the lettuce aphid was found in New Zealand and Australia.

Lettuce aphids can colonize lettuce plants at any plant stage and feed preferably from younger leaves. Large amount of aphids on the plant are able to reduce plant growth and deform the shape of the head so that the lettuce heads are then not marketable. The presence of high amount of aphids in lettuce heads is a reason for retailers to refuse to buy lettuce from growers. At young plant stage, it is possible to control the lettuce aphid using insecticide. Several products were reported efficient to control aphid population. However, resistance to chemicals were reported in some aphid population. Moreover, at maturity, it is not possible to control aphid using insecticide because the chemical product cannot enter the lettuce head. One of the most valuable strategies to control lettuce aphids is the genetic resistance. Extensive genebank screening was performed and some Lactuca virosa accessions were found completely resistant to Nasonovia rihisnigri. However, Lactuca virosa is in the second gene pool of the Lactuca germplasm according to the definition of Harlan. Therefore, these interspecific crosses are sterile, and the use of bridge species (as Lactuca serriola) was necessary to transfer the resistance into L. sativa. Genetic analyses showed that the resistance to Nasonovia rihisnigri was controlled by a single dominant gene (Nr gene) in a Lactuca sativa background.

However, breeders experienced that the release of varieties resistant to lettuce aphid was not

straightforward. The r-resistance gene was found tightly linked to recessive genes conferring strong pleiotropic effect. Such plants showed a reduced growth, a pale green colour and a lack of fertility in seed set. Using large- sized progeny and molecular markers enabled Rijk Zwaan lettuce breeders to find resistant recombinant plants without the negative side-effect phenotype.

After this finding, the release of varieties resistant to Nasonovia became more and more important. The resistance trait became a major requirement for outdoor lettuce production for the processing industry and also for the fresh market. More recently, partial resistance to

Nasonovia was reported in one L. serriola accession PI 491093 (Mc Creight, 2008)

In 2007, populations of lettuce aphids able to infect varieties resistant to Nasonovia rihisnigri were found in 4 distinct areas in Europe (France, Germany,

Belgium and Austria) . Four isolates (2 from France and 2 from Germany) were analysed further by Naktuinbouw (Netherlands Inspection Service for Horticulture) and they concluded the existence of a new Nasonovia ribisnigri biotype. This biotype is officially named Nr : 1 and is able to overcome the Nr resistance gene. Nr : 0 biotype can still be efficiently controlled by the Nr gene. Naktuinbouw also reported that IVT 280, the original source of the Nr : 0 resistance, was susceptible in their tests.

After the breakthrough of the Nr gene by the Nr : 1 biotype in practice, there was a need to find a resistance to the Nr : 1 biotype.

In the research leading to the present invention new lettuce plants were developed which are resistant against Nr : 1. The resistance was surprisingly found in Lactuca serriola . L. serriola was never reported being resistant to Nasonovia ribisnigri.

The present invention thus provides a lettuce

(Lactuca sativa L.) plant, which has the Nr : 1 resistance as found in plants grown from seeds of seedlot 10G.913569 representative seeds of which were deposited on 29 September 2010 with NCIMB Ltd, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA, UK under deposit accession number NCIMB 41763.

The invention also relates to the use of L. serriola as a source of resistance against Nasonovia ribisnigri biotype 1 (Nr:l) . The source of resistance is suitably introduced in susceptible lettuce plants (L. sativa) by introgression .

The invention further relates to Lactuca sativa plants that are resistant against Nasonovia ribisnigri biotype 1 (Nr:l), obtainable by crossing a L. serriola plant with a Lactuca sativa plant. According to a further aspect thereof, the

invention provides progeny of the plant as claimed, seeds of the plant as claimed and parts of the plant as claimed.

In one embodiment, the invention relates to a lettuce plant resistant against Nr:l, wherein said

resistance is obtainable by introgression from a plant of which representative seed was deposited with the NCIMB under accession number NCIMB 41763.

In one embodiment, the invention relates to a lettuce plant resistant against Nr:l, wherein said trait is introgressed from a plant of which representative seed was deposited with the NCIMB under accession number NCIMB 41763. "Introgression" as used herein is intended to mean

introduction of a Nr : 1 resistance into a plant not carrying the Nr : 1 resistance by means of crossing and selection.

Introgression is not limited to one cross only but

encompasses the minimum number of generations needed for the plant to become resistant, preferably stably resistant.

In one embodiment the invention relates to a lettuce plant resistant against Nr:l, obtainable by crossing a lettuce plant susceptible to Nr : 1 with a plant of which representative seeds was deposited with the NCIMB under NCIMB accession number 41763 and selecting preferably in the F2 progeny of the cross for plants being resistant against Nasonovia ribisingi biotype 1 (Nr:l) .

In one embodiment, the invention relates to a lettuce plant resistant against Nr : 1 , which plant is

obtainable by crossing a lettuce plant with a plant grown from seedlot 10G.913569 representative seeds of which were deposited with the NCIMB under NCIMB accession number 41763 and selecting in the F2 progeny of the cross, which is obtained after selfing the Fl, for plants being resistant against Nasonovia ribisingi biotype 1 (Nr:l) . The resistance trait as present in the deposited material is transferred in a pattern consistent with

recessive inheritance, and selection is thus suitably made in the second generation (F2) after having selfed the Fl .

In one embodiment, the invention further relates to a lettuce plant resistant against Nr:l, wherein when said plant is homozygous for said trait and said plant homozygous for said trait is crossed with a tester plant homozygous for the said trait, plants of the first generation progeny resulting from said cross show a 1:0 segregation for

resistance against Nr : 1.

In one embodiment, when said plants of said first generation progeny are self-pollinated, plants of the resulting second generation progeny show a 1:0 segregation for resistance against Nr : 1. In one embodiment, the tester plant is a lettuce plant grown from seeds deposited with the NCIMB under NCIMB accession number 41763.

In one embodiment, the tester plant is a plant grown from seeds deposited with the NCIMB under NCIMB accession number 41763, or a progeny of said plant which is resistant against Nr : 1.

In one embodiment, the lettuce plants of the invention do essentially not show any negative pleiotropic effects .

The invention further relates to seed of the lettuce plants of the invention and to other parts of the plant that are suitable for sexual reproduction, i.e.

propagation material. Such parts are for example selected from the group consisting of microspores, pollen, ovaries, ovules, embryo sacs and egg cells.

In addition, the invention relates to parts of the plant that are suitable for vegetative reproduction, in particular cuttings, roots, stems, cells, protoplasts, and tissue culture of the lettuce plants of the invention. The tissue culture comprises regenerable cells. Such a tissue culture can be derived from leaves, pollen, embryos,

cotyledon, hypocotyls, meristematic cells, roots, root tips, anthers, flowers, seeds and stems.

The invention also relates to progeny of the lettuce plants of the invention. Such progeny can be

produced by sexual or vegetative reproduction of a plant of the invention or a progeny plant thereof.

The regenerated progeny plants have the same genetic basis for resistance against Nr : 1 as the plant of which representative seed was deposited under NCIMB

accession number NCIMB 41763. This means that in case the genetic basis is homozygous such progeny has the same characteristics as claimed for the lettuce plants of the invention. In case the genetic basis is present in

heterozygous form, the progeny does not show resistance against Nr : 1 as is present in the plant of the invention, but still contains the alleles responsible for the Nr : 1 resistance, and is therefore still a source for Nr : 1

resistance .

In addition to this, the plant may be modified in one or more other characteristics. Such additional

modifications are for example effected by mutagenesis or by transformation with a transgene. Alternatively,

modifications in characteristics other than the Nr : 1

resistance can be introduced by introducing the Nr : 1

resistance in a different background. In the first case the resistant plant is taken as the original plant and modified. In the latter case the resistance is transferred to another plant, in particular a susceptible plant.

As used herein the word "progeny" is intended to mean the offspring or the first and all further descendants from a cross with a plant of the invention that is Nr : 1 resistant. Progeny of the invention are descendants of any cross with a plant of the invention that carries the Nr : 1 resistance. Progeny plants are preferably also resistant.

"Progeny" also encompasses plants that carry the

Nr : 1 resistance of the invention which are obtained from other plants of the invention by vegetative propagation or multiplication .

In one embodiment, the invention relates to lettuce plants that carry the trait of the invention, being

resistant against Nr:l, and having acquired said trait by introduction of the genetic information that is responsible for the trait from a suitable source, either by conventional breeding, or genetic modification, in particular by

cisgenesis or transgenesis . Cisgenesis is genetic

modification of plants with a natural gene, coding for an (agricultural) trait, from the crop plant itself or from a sexually compatible donor plant. Transgenesis is genetic modification of a plant with a gene from a non-crossable species or a synthetic gene.

In one embodiment, the source from which the genetic information is acquired is formed by plants grown from the deposited seeds or sexual or vegetative descendants therefrom.

The invention, furthermore, relates to hybrid seed and to a method of producing hybrid seed comprising crossing a first parent plant with a second parent plant and

harvesting the resultant hybrid seed. In order for the hybrid seed to express the Nr : 1 resistance of the invention, at least one of the parent plants need to be homozygous for the Nr : 1 resistance but is not necessarily uniform for other characteristics . The invention also relates to the germplasm of plants of the invention. The germplasm is constituted by all inherited characteristics of an organism and according to the invention encompasses at least the trait of the

invention, being the resistance against Nr : 1.

The invention further relates to cells of the lettuce plants are resistant against Nr : 1. Each cell of such lettuce plants carries the genetic information that leads to phenotypic expression of said trait. The cell may be an individual cell or be part of a lettuce plant or lettuce plant part.

The invention further relates to the head of a lettuce plant as claimed. The invention further relates to a food product, comprising the lettuce head or parts thereof. In particular, the food product comprises leaves of the lettuce plant or parts thereof. The food product is for example a salad or a salad mixture comprising leaves of the lettuce plant of the invention.

In this specification the term "Nr : 1 resistance" is intended to mean having the genetic information (in

particular a gene, genes, locus, loci, allele or alleles) that in homozygous state leads to the plant no longer being susceptible to Nasonovia ribisnigri biotype 1 (Nr:l) and which resistance is as found in plants of which

representative seeds were deposited under accession number NCIMB 41763, in particular in plants grown from the

deposited seeds.

The invention will be further illustrated in the following example.

EXAMPLE

Protocol of the young-plant test In order to test whether a plant is resistant to Nr : 1 the following test is performed.

Seeds are sown in potting compost blocks. Twenty plants per line were evaluated. The young plants are

inoculated 2 weeks after sowing by pouring aphids of the Nr : 1 biotype on the top of the plants. One week after inoculation, the test is scored. The second and final score occurs two weeks after inoculation. Nasonovia ribisnigri isolates

The Nr : 1 isolate used in this example was sampled in 2007 from Koningen (Germany) on a Nr : 0 resistant variety Estelle (Nunhems) : sample 279. The aphid isolate is

maintained on the variety Kitare (Nr:0 resistant variety, Rij k Zwaan) .

Introduction of the Nr : 1 resistance into susceptible lettuce

A cross between a susceptible lettuce variety L. sativa used as a female and L. serriola used a male was performed. The Fl seeds were sown and the F2 generation was obtained. After this, 150 F2 seeds were sown and propagated to generate 150 F3 lines. From these, 100 F3 lines were included in Nr : 0 and Nr : 1 tests.

The F3 line 09D.857022 was found resistant in 2008 (in test 08D.846) and the results were confirmed in 2009 (in test 09D.846) . From the test 08D.846, 3 resistant plants were selected. This F3 line was also tested against Nr : 0 twice and this line displayed a susceptible reaction. The 3 F4 lines resulting from the 3 resistant F3 plants (09D.861266, 09D.861267 and 09D.861268) were then tested against Nr : 1 in test 09D.841 and the 3 lines displayed a resistant behaviour. From 09D.861266, 4 F5 plants were selected. Those 4 F5 lines (09D.873417, 09D.873418, 09D.873419 and 09D.873420) were then included in test 09D.846 and all of them displayed a resistant reaction. From line 09D.874317, 10 plants were selected from this test. The 10 F6 lines were tested in 10D.831 and all the lines were detected resistant. The 10 lines were bulked to obtain a seed lot for a seed deposit, 10G.913569.

Nr : 1 resistant L. sativa 10G.913569 plants (called herein "the donors") were used to introgress the Nr : 1 resistance into susceptible lettuce varieties.

The donors were crossed to a cultivated susceptible lettuce variety. Cultivated varieties belonging to different lettuce types were used. The Fls obtained were selfed. Then, the different F2 populations were placed in a Nr : 1 disease resistance test as described above. At the end of the test, Nr : 1 resistant plants were selected for further development.

Claims

1. A lettuce plant (Lactuca sativa L.) resistant against Nasonovia ribisingi biotype 1 (Nr : 1 ) representative seeds of which were deposited under NCIMB accession number 41763.

2. Lettuce plant as claimed in claim 1, obtainable by crossing a lettuce plant with a plant grown from seeds of seedlot 10G.913569 representative seeds of which were deposited with the NCIMB under NCIMB accession number 41763 and selecting preferably in the F2 progeny of the cross for plants being resistant against Nasonovia ribisingi biotype 1 (Nr : 1) .

3. Lettuce plant as claimed in claim 1 or 2, being resistant against Nr : 1 as compared to a susceptible control plant, and which plant is obtainable by crossing a lettuce plant with a plant grown from seeds of lettuce plant

10G.913569 representative seeds of which were deposited with the NCIMB under NCIMB accession number 41763 and selecting in the F2 progeny of the cross that is obtained after selfing the Fl for plants being resistant against Nr : 1.

4. Seed of a lettuce plant as claimed in any one of the claims 1-3.

5. Progeny of a plant or seed as claimed in any of the claims 1-4, which is resistant against Nr : 1.

6. Propagation material of a plant as claimed in any one of the claims 1 to 5, suitable for sexual

reproduction, in particular microspores, pollen, ovaries, ovules, embryo sacs and egg cells.

7. Plant parts of a plant as claimed in any one of the claims 1 to 5, suitable for vegetative reproduction, in particular cuttings, roots, stems, cells, protoplasts, and tissue culture.

8. Head of a lettuce plant as claimed in any one of the claims 1-5.

9. Food product, comprising the lettuce head of claim 8 or parts thereof.

10. Food product as claimed in claim 8, wherein the parts are leaves or parts thereof.

11. Use of Lactuca sativa 10G.913569,

representative seeds of which were deposited under NCIMB accession number 41763, in breeding to confer resistance against Nasonovia rihisnigri biotype 1 (Nr:l) to plants that are susceptible to Nasonovia rihisnigri biotype 1 (Nr:l) .