1a.Objectives (from AD-416):
The goal of this project is to discover molecular markers for resistances to both Sclerotinia head rot and Sclerotinia stalk rot by exploiting the available molecular technology of single nucleotide polymorphisms (SNPs). A second goal is to determine whether markers for Sclerotinia resistance are near loci involved in Phomopsis stalk rot resistance. Sclerotinia attacks all parts of the plant including the root, stalk, and head, and causes heavy economic losses in sunflower. Likewise, Phomopsis also attacks the stalks of sunflower, and has caused large losses in recent years. Resistance in all cases is assumed to be quantitative in nature.
1b.Approach (from AD-416):
Phenotypic data has been gathered on 260 lines in an association mapping population for the diseases of Sclerotinia head rot, Sclerotinia stalk rot, and Phomopsis stalk rot in inoculated, multi-location field trials over the last several years. At the same time, a public-private initiative to develop SNP markers has resulted in 8700 markers which can be used for dense coverage in association mapping experiments. All 260 lines were genotyped during the marker discovery work. Sunflower data will be mined using in silico techniques to determine the location of Phomopsis and Sclerotinia resistance QTL, and compared to known QTL and candidate genes for resistance to Sclerotinia.
Work continues on mapping of Sclerotinia head rot and Phomopsis diseases. We expect that this work will be completed in the next several months. Meanwhile, Sclerotinia stalk rot resistance has been mapped to 27 different loci, 25 of which were at sites that provided quality SNP genotypes across a wide variety of backgrounds outside our mapping population. This work is currently in draft for publication later this year.