Effect of amino acids and organic acids on the sexual reproduction of species of Phytophthora and Pythium

Abstract

The effect of sterols added to various media in stimulating oospore production by Phytophthora heveae, P. cactorum and Pythium butleri was demonstrable when aspartic acid, glutamic acid and amine asparagine were the nitrogen sources, but not when leucine, isoleucine, norleucine, valine, norvaline, etc. were used. Of the postulated degradation organic acid products of this latter group, valeric, butyric, and propionic acids proved toxic over a range of concentrations, though the dicarboxylic acids were not. These findings, together with the isolation of valeric acid from a medium containing leucine, suggest that the failure of sexual reproduction in media containing leucine and valine might be due to accumulation of such toxic organic acids.