THE ROLE OF Pythium aphanidermatum AND Phytophthora melonis IN ROOT AND CROWN ROT ON GREENHOUSE CUCUMBER IN YASOUJ

In recent years, cucumber crown and root rots have been observed in greenhouses of Yasouj. In order to isolate the pathogenic agents, tissues from infected parts were cultured and twenty five isolates were recovered. Based on the morphological characters and temperature requirements, two species, namely, Phytophthora melonis and Pythium aphanidermatum were identified. Pathogenicity tests of Ph. melonis and P. aphanidermatum on different cultivars of cucumber were done under greenhouse conditions. The inoculating of crown and root systems was conducted by inoculum on vermiculite – hemp seed extract. Eventually, indices including colonization of root & crown, and seedling death were measured. It was shown that Fadia and Bahman cultivars were the most susceptible and Mehr and Close cultivars were the least susceptible in reaction to Ph. melonis, respectively. In reaction to P. aphanidermatum, Mehr and Katrina cultivars were the most susceptible for crown colonization and also Katrina cultivar was the most susceptible for root colonization.