Effects of Trichoderma on sexual reproduction of some species of Pythium and Phytophthora

Abstract

Pythium and Phytophthora cultures were subjected to volatile products from cultures of several Trichoderma spp., as well as to killed mycelium and extracts therefrom. Oospores were produced by Pythium acanthicum and P. arrhenomanes and by one strain of each of the compatible heterothallic pairs of P. sylvaticum and P. catenulatum tested, only in the presence of a suitable sterol. The volatile products of the Trichoderma spp. tested had no apparent effect on oospore production. Direct contact with Trichoderma mycelium, or fat-solvent extracts of such mycelium, resulted in oospore production by P. acanthicum. Such oospore production was likely due to the presence of sterols in the Trichoderma. Similarly, with the compatible pairs of Phytophthora cinnamomi tested, oospores were produced by paired cultures or, in some cases, by the 'A2' strains alone, only in the presence of a suitable sterol, whether or not volatile products from Trichoderma cultures were provided to the growing organisms.