DISTRIBUTION OF RACES OF HETERODERA-GLYCINES IN THE CENTRAL UNITED-STATES

A total of 62 populations of Heterodera glycines were collected in 10 states along the Mississippi and Missouri rivers, and 206 populations were collected in Arkansas. ;Among the 62 populations, races 2, 3, 4, 5, 6, 9, and 14 were found south of 37 degrees N latitude, and races 1 and 3 were found north of 37 degrees N latitude. In Arkansas samples, races 2, 4, 5, 6, 9, and 14 comprised 87% of the populations. In both groups of samples, H. glycines populations with genes that enabled th e population to parasitize cv. Pickett occurred the most frequently, f ollowed by those with genes for parasitism of cv. Peking, then PI88.78 8, and the fewest with genes for parasitism of PI90.763. The diversity of races in this study raises questions about the effectiveness of ra ce-specific cultivars for the management of soybean cyst nematodes. Th e greater diversity of races of H. glycines in the southern United Sta tes may be because of a longer history of planting resistant cultivars .