Hatching of potato cyst nematodes in root diffusates collected from twenty-five potato cultivars

Root diffusates were collected from pot-grown plants of 25 potato cultivars by leaching the soil with distilled water. The activities of the leachates collected in this way were assayed by exposing cysts of the Ro1 population of Globodera rostochiensis (Wollenweber) Behrens and the Pa3 population of G. pallida (Stone) Behrens to a geometric series of dilutions of the leachates and counting the numbers of juveniles that hatched. ‘Log activity’ values for the diffusates were computed: whereas the diffusates from most cultivars hatched G. rostochiensis well, some hatched G. pallida well and some hatched it poorly. The implications of this difference for the distribution of the two species of nematodes and for the relative tolerance of potato cultivars in the field are discussed.