Reaction of cucurbit cultivars to Phytophthora melonis and P. drechsleri under green house condations

Phytophthora drechsleri Tucker which earlier was considered to be responsible for cucurbit root rot in various parts of the world including Iran is similar to P. melonis Katsura in terms of morphology and and temperature requirement. The objective of the present study was to compare pathogenicity and reaction of both species on 87 species and vareties of cucurbits including cantaloupe, long melon, cucumber, watermelon, squashes and pumpkin. Two month old cucurbit seedlings were inoculated with 4-6 week old inoculum of both species grown on vermiculate supplemented with hemp seed extract and evaluated after two months under green house conditions. The result showed that none of the cucurbit species infected with P. drechsleri and indicated that P. melonis is one of the major cucurbit root rot in Iran. The reaction of cucurbit species and cultivars showed that cantaloupeis the most susceptible host to P. melonis. Long melon and cucumber were less susceptible cucurbita species and watermelon was more resistant than other cucurbits used.