Characterization of Phytochemicals Stimulatory to Sexual Reproduction in Phytophthora Cactorum and P. parasitica

Abstract

Phytophthora cactorum and P. parasitica formed oospores on basal medium supplemented with corn oil or crude soybean lecithin. The non-saponifiable fraction from these two supplements were stimulatory to oospore formation of both fungi, but the saponifiables were stimulatory to only P. cactorum. When the non-saponifiables were subjected to Florisil column chromatography, the fraction eluted with 25% diethyl ether in hexane was the most stimulatory. Thin layer chromatography (TLC) separated this fraction into three active bands. Among them, the two non-digitonide TLC bands were further separated by high performance liquid chromatography (HPLC), and the active fractions were isolated for gas chromatography-mass spectrometry (GC-MS) analysis. Compounds identified were 3-eicosyne, β-farnesene, tetradecane (2, 6, 10-trimethyl), docosane, hexadecanol (2-methyl), phytol, and pentatriacontane. Commercially available phytol tested was found to be highly stimulatory to oospore formation of both fungi. It was active even at the concentration of 1 ng/basal medium disc.