Sexual reproduction by Phytophthora macrochlamydospora: a group VI species

Abstract

The description of Phytophthora macrochlamydospora J.A.G.Irwin is emended, following further taxonomic studies with additional isolates of the organism. Phytophthora macrochlamydospora is a Group VI Phytophthora species, producing non-papillate sporangia, and sex organs in paired culture with Phytophthora cambivora (Petri) Buisman, A₁ mating type. Sex organs have never previously been described for P. macrochlamydospora, and this research has shown that P. cambivora A₁ induces selfing in P. macrochlamydospora. Antheridia of P. macrochlamydospora are always amphigynous. Phytophthora macrochlamydospora produces large (up to 90 µm), thick-walled chlamydospores that distinguish it from all other Group VI species.