Microflora associated with urediniospores of Uromyces viciae-fabae and effects on urediniospore germination

Abstract

The associated microflora of urediniospores of Uromyces viciae-fabae on broad bean differed quantitatively rather than qualitatively from that of broad bean ( Vicia faba L.) leaves alone. Gram-negative bacteria predominated with urediniospores whilst Cryptococcus yeasts were the most abundant micro-organisms on leaves. Rust-infected broad bean leaves supported much higher numbers of micro-organisms than uninfected leaves. Growth of germ tubes of U. viciae-fabae urediniospores was appreciably reduced on previously-wetted broad bean leaves compared with previously dry leaves. Bacteria isolated from urediniospores reduced growth of germ tubes and one isolate prevented germination on leaves. Growth of urediniospore germ tubes was greatly stimulated in the presence of Cryptococcus and Sporobolomyces yeasts and by Aureobasidium pullulons . Stimulation was more marked on glass than leaves. Trichoderma viride and Penicillium sp. also stimulated growth of urediniospore germ-tubes but to a lesser extent than the yeasts.