Abstract
In 1968, a resistant variety of sweet potato (Norin No.2) was found severely infested by a root-knot nematode originated from Miyazaki, Japan, in pots where this variety had been planted continuously for ten years. This nematode, keyed out to Meloidogyne incognita by the examination of the perineal pattern as well as host reaction test, was proved to be a new pathotype breaking resistance of another two sweet potato resistant varieties tested. As a preliminary trial, some physiological techniques were introduced to differentiate two pathotypes, resistance-breaking and ordinary one. No significant differences were indicated by the infrared absorption spectra of freeze-dried nematodes, and by the disk electrophoretic protein patterns of adult females, but the immuno-diffusion technique appeared to be promising for the purpose.
