GENETIC AND MOLECULAR CHARACTERIZATION OF RESISTANCE TO HETERODERA-GLYCINES RACE ISOLATE-1, ISOLATE-3, AND ISOLATE-5 IN PEKING

Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, has caused severe damage to soybean [Glycine max (L.) Merr.] worldwide since its discovery in 1954. 'Peking' is one of the most important sources in br eeding SCN resistant soybean cultivars because it is resistant to Race s 1, 3, and 5. Genetic information on SCN Races 1, 3, and 5 from Pekin g is essential to efficiently develop resistant soybean cultivars. Res istance to Race 3 in Peking was found to be controlled by three genes, but little is known on the inheritance of resistance to Races 1 and 5 , and whether alleles conditioning resistance to Races 1 and 5 belong to the same linkage group and are allelic to genes giving resistance t o Race 3. To determine the genetic bases of resistance to SCN Races 1, 3, and 5, Peking was crossed to the susceptible line 'Essex' to gener ate F-1 hybrids. The F-2 population and F-2:3 families were advanced f rom the F-1 and evaluated for resistance to SCN Race isolates 1, 3, an d 5. Resistance to H. glycines Race isolates 1, 3, and 5 in Peking was found to be conditioned by three genes, one dominant and two recessiv e (Rhg, rhg, rhg). Peking may share similar sets of resistance loci be tween Races 1 and 3, but not between Races 3 and 5, or between Races 1 and 5.