Mating Types of Phytophthora capsici Leonian, the Causal Fungus of Pumpkin Rot in Hokkaido

Abstract

Phytophthora rot of pumpkins (Cucurbita maxima, cultivar Ebisu) was observed in Ikeda and Shibetsu, Hokkaido in 1974 and 1975 respectively. Based on morphological, physiological, and pathological characters, the causal fungi were identified as Phytophthora capsici Leonian. All 50 single zoospore cultures of Ikeda isolate behaved as A1 compatibility type. Twenty-eight of 30 single zoospore isolates of Shibetsu fungus, soon after isolation, produced no oospore and behaved as A2 type. But after they were stocked for 18 months (transferred at intervals of 5-6 months), abundant oospores were formed, usuaIly in sector(s) or around initial inoculum when subcultured on V-8 agar plates, incubated at 23C in the dark for 10 days. The other two isolates usually produced oospores in segment(s); one, 15 days after isolation, another, after stocked for 28 months. Sterile areas acted as A2 compatibility type.