Abstract
Single egg mass of the root-knot nematode (Meloidogyne incognita) was collected from three districts in which different crops were cultivated. Each population, reproduced on a susceptible variety of tomato for three or four generations, was inoculated to resistant and susceptible varieties of tomato, sweet potato and tobacco at different temperatures (25 to 33°C). Root-knot index of two populations on three crops was higher on the susceptible varieties than the resistant ones at these temperatures, and it was raised by higher temperature. The Oami population, however, indicated a high root-knot index only on resistant variety of tomato as well as on a susceptible one. Reaction on other crops was similar to the other two populations. The parasitic ability to resistant variety in successive generations of which reproduced on resistant variety at higher temperature rose apparently in Genshu population to tomato and in Kaijyo population to sweet potato. Finally parasitic ability to resistant variety of two populations developed as same as to susceptible one under lower temperature.
