MULTIPLICATION OF ENGLISH ISOLATES OF POTATO PALE CYST-NEMATODE, GLOBODERA-PALLIDA, ON POTATOES OF DIFFERING NEMATODE RESISTANCE AND THE IDENTITY OF POTATO CYST-NEMATODE POPULATIONS

In pots, 25 populations of potato pale cyst-nematode, Globodera pallida Stone, differed significantly in their ability to multiply on potato clones P55/7 and ZC83/6, both fully resistant to G. pallida pathotype Pal. Neither clone was fully resistant to any of the populations. For 21 populations common to this and an earlier experiment, increase on the more resistant potatoes (P55/7, ZC83/6, cvs Sante, Paladin and Glenna) was correlated with their increase on less resistant potatoes (cvs Morag, Fingal and Valiant). Variation in virulence on these partially resistant potatoes was not matched by differences in the electrophoretic patterns of the nematodes' proteins. The identification of populations of G. rostochiensis (Well.) Skarbilovich used in these experiments was confirmed by electrophoresis. All populations of G. pallida Stone, appeared to contain very small numbers of G. rostochiensis after subculture on susceptible potatoes (cv. Desiree).