Specificity of cytoplasmic and cell-wall antigens from four species of Phytophthora.

Cytoplasmic and cell-wall antigens and antisera were prepared from four Phytophthora species, and cell-wall antigens were prepared from two Pythium species. Immunodiffusion of the Pythium and Phytophthora cell-wall antigens showed that the two Pythium species did not cross-react with the Phytophthora cell-wall antisera. Immunodiffusion analysis of both cell-wall and cytoplasmic antigens of Phytophthora revealed some degree of specificity between species but not between A1 and A2 mating types in Phytophthora cinnamomi. Species specificity was improved by using indirect fluorescent antibody techniques and by the use of cross-absorbed sera. Agglutination and quantitative precipitation techniques did not significantly improve specificity. It was possible to distinguish serologically between Phytophthora cinnamomi and Phytophthora cambivora and the Phytophthora cryptogea-Phytophthora drechsleri group. The absence of consistent serological variation between P. cryptogea and P dreschsleri is consistent with the suggestion (Bumbieris, 1974) that P. cryptogea and P. drechsleri should be considered as one species.