Genetic Mapping of QTLs Underlying Partial Resistance to Sclerotinia sclerotiorum in Soybean PI 391589A and PI 391589B

Soybean [Glycine max (L.) Merr.] PI 391589B, a selection from PI 391589A was recently identified as a new source of resistance to Sclerotinia sclerotiorum (Lib.) deBary, which causes Sclerotinia stem rot. The objective of this study was to identify the quantitative trait loci (QTLs) associated with resistance to S. sclerotiorum in PIs 391589A and 391589B. BC1F4:5 and BC1F4:6 populations from a cross of 'Kottman'(2) x PI 391589A and a population of F2-derived lines from a cross of PI 391589B x IA2053 were evaluated for resistance to S. sclerotiorum in the field and in the greenhouse from 2003 to 2005 and genotyped with simple sequence repeat markers. Single factor analysis identified 18 markers on nine linkage groups (LGs) significantly (P < 0.05) associated with resistance to S. sclerotiorum in the two populations. Four regions on LGs E, F, M, and O were significantly associated with the disease resistance in both populations. The four regions are between Satt411 (12.9 cM) and Satt369 (56.2 cM) on LG E, between Satt269 (11.4 cM) and AW186493 (21.0 cM) on LG F, between Satt463 (50.1 cM) and Satt323 (60.1 cM) on LG M, and between Satt581 (106.0 cM) and Satt153 (118.14 cM) on LG O on the soybean composite map developed by Song and others in 2004. Composite interval mapping identified seven QTLs (P < 0.10), each explaining 6.0 to 15.7% of the phenotypic variance. A QTL on LG M near marker Satt463 (50.1 cM) is unique to PI 391589A and B. Therefore, PIs 391589A and 391589B offer breeders a new allele for resistance to the disease.