2008 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. A total of 406 Brassica rapa plant introductions have been screened for their reaction to Sclerotinia sclerotiorum using the petiole inoculation technique (PIT) under greenhouse and field conditions. The screening process was conducted in three stages; in the first stage all accessions were evaluated. In the second stage, plants from the best 10% were inoculated a second time in the greenhouse and the accessions were taken to the field as well. Four accessions were identified as the best materials based on greenhouse and field evaluations. Of these accessions, individual plants that survived the greenhouse inoculation in this stage were then self-pollinated. Of these, S1 seeds from accessions 426281, 163497, 175050, and 21738 were advanced to the final screening stage. In the third and final stage PI 426281 had the highest survival rate at 17% compared to 7% survival rate for Hyola 357 Magnum, the resistant commercial control. Plants from this accession that survived the inoculation will produce S2 seeds, and this procedure will be continued until S4 seeds are produced. Progeny from elite crosses between B. napus accessions identified as resistant to S. sclerotiorum are being evaluated under greenhouse conditions using the petiole inoculation technique. Field trials have been planted to evaluate 35 elite NDSU breeding lines with herbicide tolerance. These lines were planted in Langdon (ND) and will be rated for Sclerotinia stem rot during the 2008 growing season,, followed by greenhouse evaluations later in the year. Production of double haploid lines is under way. The production system has been refined and 100 calli materials have been produced. These plantlets will be evaluated for tolerance to oxalic acid before being transplanted to greenhouse pots. Elite B. napus materials previously identified as having superior levels of resistance to S. sclerotiorum were used in crosses. F2 seeds from 4 of these crosses have been evaluated and surviving plants are being self-pollinated. Seeds produced by these lines will be inoculated in the winter months of 2009. 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. Publications: Zabala, F. 2008. Screening the USDA-NGRP Brassica rapa collection for resistance to Sclerotinia sclerotiorum. MS Thesis, North Dakota State University. 68 p.