Mapping soybean QTL conferring resistance to Phytophthora sojae through different phenotypic methods and assessment of their contribution to yield
H. WANG (1), S. K. St. Martin (2), A. E. Dorrance (1)
(1) The Department of Plant Pathology, The Ohio State University, Wooster, OH, U.S.A.; (2) The Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH, U.S.A.
Phytopathology 101:S186

Partial resistance to Phytophthora sojae in soybean is expressed as reduced infection efficiency, smaller root lesions and reduction in oospore production. This type of resistance is conferred by several quantitative trait loci (QTL). In several host-pathosystems, individual QTL have been reported to be effective towards specific pathogen isolates or influenced by environmental conditions. In addition, the contribution of QTL towards yield is an important factor for selecting QTL candidates for resistance breeding. In this study, QTL in the ‘Conrad x Sloan’ F_4:6 population were mapped against three P. sojae isolates using two greenhouse phenotyping assays. Soybean QTL with smaller effects, especially those which originated from the susceptible parent, were not consistently detected among isolates or between phenotyping assays. Of the ten QTL mapped, four QTL on Chrs. 18 and 19 from Conrad had the largest effects and were detected with all three isolates and both phenotyping assays. The RILs with resistant alleles from these four QTL had significantly higher yield than RILs with susceptible alleles. These results indicate the important role of these four QTL in conferring partial resistance to P. sojae populations as well as their contribution towards overall yield.