Abstract
When (+) and (-) isolates of Pythium splendens were paired on the opposite sides of a polycarbonate membrane, oospores were produced by (+) but not (-) isolate. In addition to the original mating type, the opposite mating type appeared in the progeny derived from selfed oospores of most (+) isolates tested. Occasionally self-fertile (±) and neuter (0) types were also detected. The self fertility nature of (±) was unstable and transitory, segregating into (+) and (-) types during asexual reproduction. It was postulated that selfing may have changed the mating type by altering the function of a repressor which regulated the expression of mating types with different molecular configuration.
