Microscopical studies of the infection of gerbara flowers byBotrytis cinerea

Abstract

The formation of lesions on ray florets of gerbera flowers caused by single conidia ofBotrytis cinerea was studied in two cultivars infected by two isolates of the pathogen. No differences in reaction after inoculation with conidia of either isolate were seen on either cultivar. The conidia produced usually one germ tube not longer than 10 μm, but conidia with five germ tubes were also seen. Direct penetration of germ tubes through the upper cuticle of ray florets was observed. No appressoria or other specialised structures were observed before penetration, and degradation of the cuticle did not occur. Germination of conidia and subsequent flower infection was dependent on the availability of free water, but not on the addition of external nutrients.