Location: Sunflower Research
2013 Annual Report
We are building on progress made on projects previously funded by the Sclerotinia Initiative. At the end of 2011 and during the winter months of 2012 we set up to increase seed of B. napuslines with resistance to S. sclerotiorum that we developed as part of our SI projects. Seeds of these lines, NEP 63, a doubled haploid line and the F6 line of Ames 26628xPI458539 were intended for field trials to be planted during the summer of 2012. We encountered difficulties in producing enough seed for evaluations in our disease nursery trials, so in 2012 we increased seed of these lines in greenhouse. Also, we successfully produced five sets of F2 seeds from the cross between NEP63 and NEP32, another doubled haploid line considered susceptible to SSR. A set containing 180 seeds from one of these crosses was planted in the greenhouse and inoculated with S. sclerotiorum using the petiole inoculation technique and also had DNA extracted. The lines evaluated segregated for time to flowering as well as for their reaction to inoculation. Lines with the highest levels of resistance and earliest times to flowering were identified and have been planted in the field for evaluation. We are awaiting results of the molecular markers work that will allow us to identify QTL associated with resistance.
Molecular markers associated with resistance to S. sclerotiorum were identified by screening the DNA of 278 B. napus accessions using 3072 DArT molecular markers. Thirty two markers were significantly associated with SSR resistance and their effects ranged between 1.5 and 4.22%. The location of some of the markers was established to chromosome level, but some could be identified only to genome level. As soon as the C genome becomes available, we will try to anchor these markers. A BLAST search indicated that 20 of the 32 DArT markers associated with resistance to S. sclerotiorum in B. napus had also been detected in the B. rapagenome. Some markers were also detected in the Arabidopsis thaliana and B. oleraceagenomes. The most resistant accessions have been identified and are being used in crosses to develop breeding populations.
Thirty three F5 lines from the cross between B. napus accessions PI458939xPI649136 were evaluated for their reaction to S. sclerotiorum and Leptosphaerica maculans, the causal agent of blackleg. Lines 71 and 153 were moderately resistant to PG-3 and PG-4 strains of L. maculans and at the same time have some resistance against S. sclerotiorum. These lines are being used to develop breeding lines.
Production of double haploids from B. rapaPI426281 and Ames 21738 is under way. We did not make crosses between our lines and elite glyphosate-tolerant lines as we had proposed due to legal limitations imposed on the NDSU breeding program; instead, we made crosses between our lines and public lines like 'Jet Neuf, 'Quantum', and `Samourai' which could be useful sources of resistance against SSR and blackleg. Glyphosate-tolerant canola breeding lines were identified as having statistically less disease than three of the four commercial controls included in the study. In 2012, Sclerotinia stem rot incidence ranged between 34% and 74% with 2 breeding lines below the 40% mark. The two best breeding lines are hybrids that had not been evaluated before.