AGAROSE MEDIUM FOR GERMINATION OF OOSPORES OF PHYTOPHTHORA-CACTORUM

When oospores of Phytophthora cactorum from 30-day-old culture were tr eated with 0.25% KMnO4 for 20 min and incubated at 24 degrees C under light for 10 days, 65-75% germinated on water agar and water agarose b ut only 1-21% germinated on V-8 agar and S+L agar. Water agarose was s elected because germinated oospores formed restricted colonies on this medium that could be isolated easily. KMnO, treatment killed sporangi a, chlamydospores and mycelial fragments present in oospore suspension s. Under the above conditions, approximately 44% of oospores from 10-d ay-old culture germinated and the optimum germination rate of about 75 % was obtained when oospores reached about 20 days old.