FACTORS AFFECTING OOSPORE GERMINATION OF HETEROTHALLIC PYTHIUM SPLENDENS

Oospores from a cross between (+) and (-) mating types of Pythium sple ndens had a germination rate of only 2-3% on nutrient media. When oosp ores from 20-day-old cultures were treated with 0.25% KMnO4 for 20 min utes, germination was increased to 49% in 2 days on a medium consistin g of mineral salts, lecithin, glucose and agar (S+L agar). Amendment o f S+L agar with 0.15% L-sorbose reduced growth but without affecting g ermination, enabling the germination rate to be determined after incub ation for 3 rather than 2 days. Germination increased with increasing age of cultures up to 30 days for all treatments. Exposure to light du ring germination also increased the germination rate of oospores matur ed either under light or in darkness. Oospores from 40-day-old culture s treated with KMnO4 for 30 minutes had a germination rate of more tha n 90% under light on S+L agar amended with L-sorbose.