Pathogenicity of the root-knot nematode Meloidogyne incognita to Vigna unguiculata.

Screenhouse experiments were conducted in 3 L pots to investigate the relationship between a range of population densities (0, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 eggs and second stage juveniles/cm(3) soil) of Meloidogyne incognita race 1 and yield of a resistant cultivar (Ojito Negro) of Vigna unguiculata. Seinhorst's yield-loss model was fitted to yield data, and confirmed that this cowpea cultivar is only slightly affected by M incognita. Cultivar Ojito Negro tolerates up to 0.74 J2 + egg of M. Incognita/cm(3) soil and at the highest population density, seed weight and dry aerial weight, were reduced only 20% and 10%, respectively. Numbers of M incognita increased in soil infested with initial population densities up to 6J2+eggs/cm(3) soil, and remained at same level at larger initial population densities. Nematode reproduction rates were inversely related to the initial population densities. Data for initial and final nematode densities were well fit by Seinhorst's model of population growth, assuming a maximum reproduction rate of 1.6, equilibrium density of 3 J2 + eggs/cm(3) soil, and maximum potential nematode populations of 6 J2 + eggs/cm(3) soil.