Some effects of fast neutron irradiation upon M̲e̲ḻo̲i̲ḏo̲g̲y̲ṉe̲ I̲ṉc̲o̲g̲ṉi̲ṯa̲ (Kofoid and White, 1919) Chitwood, 1949

Two groups of Meloidogyne incognita (Kofoid and White, 1919) Chitwood, 1949 eggs (Stage I = 50% of total number of eggs at a stage of embryological development exceeding the four-cell stage; Stage II = 50% of total number of eggs at a stage of embryological development equal to or less than the four-cell stage) were irradiated at 7, 22, and 32°C with 0, 1, 2, 3, or 4 Kilorads (Krads) of fast neutrons. Radiation treatment had an effect on the hatch of both Stage I and Stage II eggs. The hatch of Stage I eggs was inversely proportional to the radiation levels and was independent of irradiation temperature. However, the hatch of Stage II eggs was not proportional and was associated with irradiation temperature. More Stage II eggs hatched at 2 Krads, 7°C treatment than at any of the other treatments at the same temperature. Significantly fewer eggs hatched at the 1 Krad treatment. The 0, 3, and 4 Krad, 7°C hatches were intermediate between and differed from the hatches at 1 and 2 Krads. At 22°C, all radiation treatments at Stage II showed significant increases over the hatch at 0 Krads with peaks at 1 and 3 Krads. The Stage I eggs followed a pattern similar to that noted at 7°C. At 32°C, the greatest number of eggs hatched at Stage I, Host differential studies showed that eggs produced by females developing from Stage II eggs receiving 1, 2, and 3 Krads at 7°C and by females developing from both Stage I and Stage II eggs receiving 1, 2, 3, and 4 Krads at 32°C developed into larvae capable of parasitizing and reproducing on a resistant variety of cowpea, Vigna sinensis 'Breeding Line M57-13N'. A change in the ability of Stage I, 7°C and Stage I, 32°C 3 Krad larvae to parasitize a normally susceptible water-melon, Citrulus vulgaris 'Charleston Grey', was noted. It was also observed that larvae developing from eggs laid by females developing from Stage I eggs exposed to 2 Krads at 7°C and from Stage II eggs exposed to 1 and 3 Krads at the same temperature were able to parasitize and reproduce on Nicotiana tabacum 'NC-95', a normally resistant variety of tobacco. Similar changes were noted in larvae developing from eggs laid by females developing from Stage II eggs exposed to 1 Krad at 32°C.