Polyploidy and Induced Gametangial Formation in British Isolates of Phytophthora infestans

Abstract

Summary: Gametangial (sex organ) formation in cultures of a British isolate of Phytophthora infestans, mating type A1, was induced by simultaneous inoculation with both A1 and A2 isolates of P. palmivora. Inoculation with the A2 mating type only was ineffective. Three isolates of P. infestans were examined: two were polyploid, of which one was probably tetraploid; the third had both diploid and polyploid nuclei. Phytophthora infestans also produced gametangia when inoculated simultaneously with both A1 and A2 types of P. cambivora and P. cinnamomi. The ecological significance of these findings is discussed.