Competition and Synergism between Cholesterol and Cholestanol in Oospore Formation in Phytophthora cactorum

Abstract

Cholesterol promoted oospore formation in Phytophthora cactorum; very few oospores were formed when cholestanol was incorporated in the medium instead. Above a critical concentration of cholesterol, cholestanol competitively inhibited oospore formation by cholesterol when both were added to the medium together. At low cholesterol concentrations, the addition of some cholestanol increased the number of oospores; further addition of cholestanol was inhibitory. Cholesterol and cholestanol stimulated vegetative growth to a similar extent.