The relative susceptibility of some cucurbits to an Iranian isolate of Phytophthora drechsleri

Abstract

When zoospores of Phytophthora drechsleri were added to a hydroponic medium in which roots of cucurbit plants were immersed, marrow and pumpkin (Cucurbita spp.) remained symptomless but cantaloup, melon and cucumber (Cucumis spp.) wilted. Symptom development was proportional to the logarithm of day number after inoculation and approximately proportional to the logarithm of zoospore number in cantaloup and melon but not cucumber which was also less susceptible. The fungus became established preferentially in the hypocotyls of cantaloups. Ten times as many chlamydospores differentiated on infected cantaloup hypocotyls as on lupin roots when both tissues were buried in moist soil.