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United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
To screen all accessions of the U.S. Brassica rapa collection for their reaction to S. sclerotiorum, and to characterize the genetic basis of resistance found in six elite B. napus plant introductions.

1b.Approach (from AD-416)
Evaluations/screening of 289 remaining Brassica rapa accessions will be conducted to identify resistance to white mold. Six plant introductions that are hightly resistant to Sclerotinia sclerotiorum will be crossed with S. sclerotiorum susceptible lines. Double haploid populations will be developed and molecular markers will be used to identify quantitative trait loci associated with resistance to the disease.

3.Progress Report

This project was initiated on June 1, 2006, research is ongoing, and the overall objective is to identify Brassica rapa breeding lines and accessions with enhanced resistance to Sclerotinia sclerotiorum as well as herbicide tolerance. ADODR monitoring activities to evaluate research progress included phone calls, meetings with the cooperator, and an annual meeting held each year in January.

Screening for improved Sclerotinia resistance in canola: A microspore culture system was developed to produce double haploid plants from B. napus accessions Ames 26628 (Ca01) and PI458939 (Ca02), and F1 lines PI458940 × PI458940 (Ca03); PI458939 × Ames26628 (Ca04); and PI458940 × Ames26628 (Ca05). Effects of genotype, donor plant condition, flower stage/bud size, and culture temperature on embryogenesis were determined. A total of 89 haploid plants from Ca01 were inoculated in greenhouse using the PIT. Of these, 36 plants survived the inoculation and had their chromosome numbers doubled using colchicine. Double haploid plants from these selections will be planted in greenhouse for seed production. Plants from Ca05 will be evaluated for their reaction to S. sclerotiorum later this year. Development of additional plants from other B. napus and B. rapa elite accessions is planned for coming years. Of 35 NDSU breeding lines evaluated in Langdon in the summer of 2008, three breeding lines (0330416, 305457, 0427681) showed statistically higher levels of resistance than commercial controls although incidence in these lines was one third of that of the controls. Two other lines (0427649, and 30522) were superior to only one of the controls. Forty five additional lines were tested in the greenhouse using the PIT. Two lines (427761 and 427765) had significantly similar levels of resistance that Pioneer 45H26 the commercial control used. This information has been shared with the breeder. Phenotypic reaction of 230 F2 plants from a cross between PI458939 and Ames 26628 (B. napus accessions previously identified as having superior levels of resistance to S. sclerotiorum) were evaluated in greenhouse conditions using the PIT. Approximately one third of the plants survived the inoculation and the group was taken to seed production by self pollination. Seeds from these plants will be evaluated in the greenhouse again later this year and plant tissue samples will be taken to extract DNA. Molecular marker work will start later this year. This project will contribute to developing canola breeding lines with herbicide tolerance in addition to improved resistance to Sclerotinia sclerotiorum. The National Sclerotinia Initiative contributes to the goals of ARS National Program 303 – Plant Diseases.

Last Modified: 11/27/2015
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