Continuing variation in successive asexual generations of Phytophthora cinnamomi following sexual reproduction

Abstract

Colony-type stability of asexual progeny of selfed-oospore cultures of Phytophthora cinnamomi was investigated. Progeny were divided into parental type A, types B to E for those different from type A but with a distinct uniform pattern, and type M for those with the overlapping appearance of two different types. Colonies derived from three successive zoospore generations of isolate P630 were of the same parental A type. However, colonies from oospores of the same isolate consisted of types A, B, C, D, E, and M. Some of the oospore cultures of type A or B and all the type M oospore cultures produced zoospores containing more than one type. Oospore cultures of types C, D, or E that were tested produced zoospores with the same colony type as their respective parent. Among the five cultures randomly selected from asexual progeny produced by oospore isolates P630-21 and P630-6, four displayed continuing variation in colony type in the three to five successive zoospore generations tested. Keywords: asexual variation, continuing variation, Phytophthora cinnamomi, sexual reproduction.