Cyst nematode resistance and seed yield of soybean lines derived from SS97-6946
New sources of resistance to the soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) would be useful for soybean [Glycine max (L.) Merr.] cultivar development. The objective of this study was to determine the relationship between SCN resistance and seed yield for a new source of SCN resistance, SS97-6946, developed by the Univ. of Missouri-Columbia. F5-derived lines were developed from the cross of SS97-6946 x S27-T7, a SCN-susceptible cultivar developed by Syngenta. Nine sets of 32 F5:8 lines each were evaluated for yield in replicated tests at five Midwest locations during 2007. The lines were evaluated for resistance to four HG types of SCN populations in growth rooms by determining their female index, which was the number of cysts on the roots of a line relative to a SCN-susceptible cultivar. There were six out of the 36 combinations of sets and HG types that had significant negative phenotypic correlations between yields of the lines and their female indexes. This indicated that the lines with the highest yield tended to have lower female indexes and greater SCN resistance, and that SS97-6946 would be a useful source of SCN resistance for soybean cultivar development.