Reversible change of mating type in Phytophthora parasitica.
In addition to the original mating type, the opposite type appeared in the zoospore population of single isolates of P. [nicotianae var.] parasitica after long-term storage or chloroneb treatment. Occasionally self-fertile zoospores were also detected, but their self-induction nature was transitory and unstable. Both hormone production and hormone reception were changed in the sexual variants. The results explain the apparent change from cross-induction (heterothallic) to self-induction (homothallic) in the fungus after long-term storage and chloroneb treatment, and suggest one possible evolutionary origin of sex in the lower fungi.