Variability in Reproduction of Four Races of Meloidogyne incognita on Two Cultivars of Soybean

Variability in the reproduction of the four races ofMeloidogyne incognita on the soybean cuhivars Pickett 71 and Centennial was studied in growth chamber experiments. Analysis of variance in the number of eggs produced by the races 6 weeks after the plants had been inoculated with 5,000 eggs of each race revealed that the nematode race by soybean cultivar interaction was highly significant (P = 0.001). Races 1, 3, and 4 produced from about 5,000 to 15,000 eggs per root system on Pickett 71 and only from about 300 to 600 eggs per root system on Centennial. In contrast, race 2 produced about 8,000 eggs per root system on Centennial and about 1,200 eggs per root system on Pickett 71. In a second experiment, in which the plants were inoculated with 2,000 second-stage juveniles, race 1 and race 2 produced about 13,000 and 3,000 eggs per root system, respectively, on Pickett 71 and about 600 and 10,000 eggs per root system, respectively, on Centennial. The results suggest that M. incognita resistance in soybean is race-specific.