Vertical distribution of parasitic nematodes in the rhizosphere (0-35 cm in soil depth) of winged bean and differences in susceptibility to root-knot nematodes among 46 winged bean varieties were surveyed in subtropical Ishigaki Island, Okinawa.
Eight nematode genera were found, and root-knot nematodes (Meloidogyne incognita and M. javanica) were most predominant. Spiral nematodes also occurred frequently, but their population levels were very low.
Vertical distribution of root-knot nematode larvae indicated a tendency that the upper soil layer contained more number of the larvae than the lower layer, although the distribution was slightly influenced by root distribution of different varieties of winged bean. It was apparent that the spiral nematode occurred in comparatively deep soil below 15 cm of depth.
A high degree of variability in the population density of root-knot nematode larvae in the rhizosphere was observed among winged bean varieties tested, i.e., 16 varieties showed a high population density, 10 varieties a moderate density, and 20 varieties a low density less than 10 larvae per 10 g of soil.