Association between SCN resistance and yield in soybean, and, QTL mapping of field resistance to Sclerotinia sclerotiorum in soybean.

摘要

Disease resistant soybean [Glycine max (L.) Merr.] cultivars have been important for the prevention of major yield losses as is the case for soybean cyst nematode (Heterodera glycines Ichinohe; SCN). There is concern, however, that SCN resistant cultivars yield less than SCN susceptible cultivars under low SCN pressure. To test for linkage of yield depression with SCN resistance, seven near isogenic line (NIL) populations segregating for plant introduction (PI) 88788 derived SCN resistance at either rhg1 or cqSCN-003 were yield tested across two years in four locations with previously low SCN incidence. Resistant NILs yielded less (alpha = 0.05) than susceptible NILs in a population segregating for rhg1 and a population segregating for cqSCN-003. Molecular marker data suggest the presence of a quantitative trait locus (QTL) for yield depression distal to rhg1 on linkage group (LG) G and another QTL distal, proximal or pleiotropic to cqSCN-003 on LG J.; Current soybean cultivars express only partial resistance to Sclerotinia stem rot [caused by Sclerotinia sclerotiorum (Lib.) de Bary] with 'Syngenta S 19-90' having one of the highest levels of resistance. Syngenta S 19-90 was crossed to the partially resistant PI 153282 and 174 F4-derived lines were tested for Sclerotinia stem rot resistance at three field locations across two years. In two environments was the Sclerotinia stem rot incidence sufficient for evaluation of disease resistance, which was measured with a disease severity index (DSI). One line had increased levels of resistance but was associated with disease escape traits. Three DSI QTL were detected (alphaE = 0.25) that were not associated with disease escape traits, suggesting that they confer physiological resistance. These QTL mapped on LGs B1, C2 and L and explained 4.1%, 4.9%, and 4.7% of the phenotypic variation, respectively. These results confirm a S. sclerotiorum resistance QTL on LG L that was previously identified with laboratory and greenhouse methods.; Confirmation and refinement of results from both studies will enable soybean breeders to use marker-assisted breeding for the development of SCN resistant cultivars with higher yield potential and the development of soybean cultivars with increased levels of resistance to Sclerotinia stem rot.