The effect of benomyl on growth and ultrastructure of two isolates of Phytophthora infestans from Egypt

The effect of benomyl as a fungicide on the growth rate and ultrastructure of two isolates (P1319 and P623) of Phytophthora infestans is compared. Ben omyl caused a concentration-dependent inhibition of the mycelial growth of both isolates. The isolate P1319 was found to be more sensitive to benomyl than the isolate P623. Ultarstructural studies confirmed these observations . The hyphae of isolate P1319 subjected to 100 and 500 ppm benomyl showed m ore severe changes in the cytoplasm than those of isolate P623. An increase in lipid bodies and vacuoles in the hyphal cytoplasm was the characteristi c phenomenon after treatment with benomyl, particularly at a concentration of 500 ppm.