DETECTING THE PRESENCE AND DISTRIBUTION OF GLOBODERA-ROSTOCHIENSIS AND GLOBODERA-PALLIDA MIXED POPULATIONS IN NEW-ZEALAND USING DNA PROBES

The distribution of the potato cyst nematode Globodera rostochiensis (Woll.) pathotype Ro1 and G. pallida (Stone) pathotype Pa2/3 in New Zealand was determined using dot-blot hybridisation with species-specific DNA probes. Both species of nematode were present in New Zealand, with the main foci in intensive cropping areas (market gardens) around the urban centres of Auckland, Christchurch, and Dunedin. A number of domestic gardens were also infested. Of the 64 populations tested, 24% were pure Ro1, 20% were predominantly Ro1 with a low frequency or trace of Pa2/3, 33% were pure Pa2/3, and 6% were Pa2/3 with a trace of Ro1. The remaining 17% contained an equal proportion of both species. The presence of trace Pa2/3 and the impact of mixed species populations on the long-term success of nematode-resistant potato cultivars is discussed.