Isozyme variability among isolates of Phytophthora cinnamomi from Australia and Papua New Guinea

Abstract

Genetic variation in 183 isolates of Phytophthora cinnamomi from a wide range of hosts and locations in Australia and Papua New Guinea (PNG) was assessed at 20 isozyme loci. Low levels of isozyme variation were found in both the A, and A2 mating types within Australia. Only two A2 multilocus genotypes were detected among Australian and PNG isolates, the more common one being found throughout the range. Fourteen of the 15 A1 isolates from 12 locations in Australia were identical at all 20 isozyme loci. In contrast there was much higher variability in the eight PNG A1 isolates compared with the Australian Ai isolates and all A2 isolates. The A1 and A2 mating types can be distinguished isozymically suggesting that they are genetically isolated and that sexual reproduction involving both mating types does not occur in the field.