Identification of QTL underlying soluble pigment content in soybean stems related to resistance to soybean white mold (Sclerotinia sclerotiorum)

The frequency of soybean white mold (Sclerotinia sclerotiorum, SWM) outbreaks has increased since 1978, and this disease is currently considered to be the second most important cause of soybean yield loss worldwide. We have studied SWM in stems of soybean cultivar Maple Arrow, which shows partial resistance to SWM, in an attempt to identify the quantitative trait loci (QTLs) underlying soluble pigment(s) content, which is associated with SWM resistance. A SWM-susceptible cultivar, Hefeng 25, was crossed with Maple Arrow, and 149 F5:6 recombinant inbred lines were subsequently advanced through single-seed-descent. A total of 109 simple sequence repeat (SSR) markers were used to construct a genetic linkage map. Three QTLs for soluble pigment content in soybean stems associated with the resistance to SWM, namely, Qsp-1 (Satt502-Sat_159), Qsp-2 (Sat_156-Satt251), and Qsp-3 (Satt525-Satt233), were identified in 2007 and 2008 and located onto linkage groups D1a+q, B1 and A2, respectively. The phenotypic variation (R2) explained by these QTLs ranged from 6.29 to 15.37%. These three QTLs were not significantly related to known QTLs associated with escape resistant mechanisms. The use of these QTLs in marker-assisted selection may contribute to improved soybean resistance to SWM.