GERMINATION AND APPRESSORIAL FORMATION BY UREDOSPORES OF UROMYCES-VICIAE-FABAE EXPOSED TO INHIBITORS OF POLYAMINE BIOSYNTHESIS

An examination was made of the effects of three polyamine biosynthesis inhibitors on germination and appressorium formation by uredospores of the bean rust fungus Uromyces viciae-fabae on artificial membranes. The ornithine decarboxylase inhibitor a-difluoromethylornithine had no effect on uredospore germination, even when used at 2mM, whereas appressorium formation was reduced by 63% at 0.5 mM and by 99% at 2 mM. Methylglyoxal bis(guanylhydrazone), an inhibitor of S-adenosylmethionine decarboxylase, reduced germination when used at 0.025 mM, and at this concentration, appressorium formation was completed prevented. Uredospore germination was unaffected by as much as 3 mM cyclohexylamine, an inhibitor of spermidine synthase, while appressorium formation was reduced at 1 mM and completely prevented at 3.3 mM. These results support previous suggestions that inhibitors of polyamine biosynthesis exert their main effect on the early stages of fungal development on the leaf surface.