Scanning electron microscopy of parasitism of Botrytis cinerea on flowers and fruits of cucumber

Abstract

Infection of female flowers of cucumber occurred within one day of inoculation with 10⁴/ml conidia of Botrytis cinerea whereas it took two days to establish infection when 10² conidia/ ml served as inoculum. Glucose enhanced the infection rate of sepals, petals and stigmata. Cucumber flowers infected with B. cinerea, studied under the SEM, showed that conidia which germinated on the petal either produced a germ-tube which extended over the surface or penetrated directly into the host tissue. Hyphae of B. cinerea also penetrated the host via natural openings. Germinating conidia produced hyphae 10–100 μm in length before penetrating the stigmata. Young fruits were penetrated either directly or via stomata. Hyphae which approach stomata may produce a swelling over the stomatal cells or may penetrate directly into the stomatal chamber. A dense mycelium was produced over the stigmata within 4 d of inoculation.