Temporal Distribution of Mating Types and Cultural Variation of Phytophthora infestans at the Volcano District on the Islandof Hawaii.

Abstract

Forty four isolates of Phytophthora infestans recovered from diseased potato leaves at the Volcano district on the island of Hawaii from 1986 to 1987 were all A1 mating type and sensitive to metalaxyl. However, all of the 23 isolates obtained from diseased tomato and potato leaves from the same area from 1994 to 1995 were all of the A2 mating type and resistant to metalaxyl. The recent isolates displayed considerable variation in growth rate and ability to produce sporangia. Substantial variation in growth rate, ability to produce sporangia and response to metalaxyl was also observed among zoospore progeny of a recent isolate tested. The possible mechanisms for the recent appearance of A2 mating type and diversity in growth rate, sporangial production and response to metalaxyl among the new population on the island of Hawaii are discussed.