One population each of Radopholus similis and R. citrophilus from Florida were screened using root explant cultures to determine their reproduction potential on the soybean (Glycine max) cultivars, Peking, Bragg, Centennial, Pickett, Lee, Kent, Essex, Bedford, Delmar, Hill, Williams, Dyer, Hood, and PI 90763. After a 5-week incubation at 25 C, counts of adults/juveniles and eggs were determined in roots that had been removed from the agar and stained in acid-fuschin. The black-seeded lines, 'Peking' and PI 90763 known to be resistant to other nematode species were highly susceptible to R. citrophilus and moderately susceptible to R. similis. Counts from the other 12 cultivars were, in general, lower for R. similis than R. citrophilus. Furthermore, by plotting of root weight to the number of eggs and mixed life stages recovered from the roots, the degree of tolerance of any of the tested soybean cultivars to the two nematode species could be determined.
