Submitted to: Proceedings of the International Sclerotinia Workshop
Publication Type: Abstract Only
Publication Acceptance Date: January 10, 2006
Publication Date: January 18, 2006
Citation: Hu, J., Radi, S.A., Gulya Jr, T.J., Miller, J.F. 2006. Progress in mapping QTLs responsible for resistance to Sclerotinia head rot and stalk rot in two segregating sunflower populations [abstract]. Sclerotinia Initiative Annual Meeting, January 18-20, 2006, Bloomington, MN. Available: http://www.whitemoldresearch.com/html/abstractdetails2.cfm?Research_ID=146 Technical Abstract: Two segregating F2 populations were developed by selfing a USDA experimental hybrid (HA 441 x RHA 439) and a proprietary commercial hybrid (Proseed 9405). These two populations were grown in three research plots during the 2005 growing season. The first plot (Mapleton, ND) was inoculated with Sclerotinia-infected millet seeds for stalk rot development under natural conditions. Only eight and ten plants out of the 192 plants developed stalk rot in Proseed 9405 and HA 441 x RHA 439 populations, respectively. The second plot (Fargo, ND) was inoculated with an ascospores solution (~5000 spores/ml) for studying head rot, which was developed under artificial misting irrigation. For disease reading, we used the zero (resistant) to five (susceptible) scoring system. The population could be divided into roughly two groups, and with a few plants scored between 1 and 4. We tested 192 plants for each population. There were 105 and 70 plants with disease scores of zero in the (HA 441/RHA 439) and Proseed 9405 F2 populations, respectively. This could be the result of the fact that the USDA hybrid possesses more resistance genes than Proseed 9405, because the former produced more resistant progeny. Between each pair of parents, about 600 high quality polymorphic TRAP markers have been scored, which will be sufficient to construct linkage maps for QTL mapping. The third plot (Fargo, ND) was for generating F3 seeds, and selfed seeds were harvested from 300 individuals for the replicated F2-F3 row field tests to locate QTLs conferring head rot tolerance in these two populations during the 2006 growing season. It will be possible to pyramid the tolerant QTLs into an elite USDA sunflower line if the two populations have different QTLs responsible for Sclerotinia tolerance.