Project Number: 5442-21000-034-04
Project Type: Specific Cooperative Agreement

Start Date: May 15, 2008
End Date: May 14, 2009

Objective:
The new objectives of this follow-on project are to 1) continue construction of a recombinant inbred line population (RIL) derived from a cross between HA 441 and RHA 439 for future confirmation of the quantitative trait loci (QTL) for head rot, and 2) evaluate some lines that performed well for Sclerotinia head rot or stalk rot resistance in the 2007 field trials.

Approach:
The primary objective of the original Specific Cooperative Agreement 58-5442-3-277 was to employ advanced molecular technology using marker-assisted selection to accelerate the process of creating sunflower germplasm with higher levels of tolerance to Sclerotinia disease. During the last two years of the project, we completed mapping of the quantitative trait loci (QTL) for Sclerotinia head rot resistance in HA 441and RHA 439, both of which are USDA sunflower lines. We accomplished this by constructing a genetic map of 18 linkage groups with 249 markers, and located nine QTL for disease incidence and seven QTL for disease severity on 10 of the linkage groups. Promising data was also obtained for Sclerotinia stalk rot tolerance. To complete the studies of the original agreement, it is now necessary to complete the construction of the RIL population from the cross of HA 441 and RHA 439. We have completed construction through the F4 generation and need to complete two more generations to obtain a usable RIL population. A new objective of this follow-on agreement will be to evaluate some of the best Sclerotinia tolerant lines we identified in the original project for release to the public. In 2008, we will 1) advance four lines derived from a cross of HA 441/RHA 439 which performed well and consistently for head rot resistance in the F5 generation in greenhouse. Head rot resistance of the four lines together with their hybrids from a cross with cmsHA 89, along with two checks will be evaluated in the field with three replicates; 2) four RIL lines from the RHA 208/RHA 801 RIL population resistant to stalk rot together with their hybrids with cmsHA89 and two checks will be re-evaluated under field conditions with three replicates; and 3) continue construction of the HA 441/RHA 439 RIL population by single seed descent method. We will sow the seeds we bagged in the field in 2007, one row for one head, bagging one head before flowering, and harvesting them for advancing to the next generation in the following year.