Identification of a new major QTL associated with resistance to soybean cyst nematode (Heterodera glycines)

Resistance of soybean [Glycine max (L.) Merr.] to cyst nematode (SCN) (Hete rodera glycines Ichinohe), one of the most destructive pathogens affecting soybean, involves a complex genetic system. The identification of QTLs asso ciated with SCN resistance may contribute to the understanding of such syst em. The objective of this work was to identify and map QTLs for resistance to SCN Race 14 with the aid of molecular markers. BC3F2:3 and F-2:3 populat ions, both derived from an original cross between resistant cv. Hartwig and the susceptible line BR-92-31983 were screened for resistance to SCN Race 14. Four microsatellite (Satt082, Sat_001, Satt574 and Satt301) and four RA PD markers (OPAA-11(795), OPAE-08(837), OPR-07(548) and OPY-07(2030)) were identified in the BC3F2:3 population using the bulked segregant analysis (B SA) technique. These markers were amplified in 183 F2:3 families and mapped to a locus that accounts for more than 40% of the resistance to SCN Race 1 4. Selection efficiency based on these markers was similar to that obtained with the conventional method. In the case of the microsatellite markers, w hich identify homozygous resistant genotypes, the efficiency was even highe r. This new QTL has been mapped to the soybean linkage group D2 and, in con junction with other QTLs already identified for SCN resistance, will certai nly contribute to our understanding of the genetic basis of resistance of t his important disease in soybean.