Polyploidy and Induced Gametangial Formation in British Isolates of Phytophthora infestans

Abstract

Gametangial (sex organ) formation in cultures of a British isolate of P. infestans, mating type A1, was induced by simultaneous inoculation with A1 and A2 isolates of P. palmivora. Inoculation with the A2 mating type only was ineffective. Three isolates of P. infestans were examined: 2 were polyploid, of which 1 was probably tetraploid; the 3rd had diploid and polyploid nuclei. P. 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.