Induction of resting spore germination in Entomophthora aphidis by long-day light conditions

Abstract

A small proportion of Entomophthora aphidis Hoffmann resting spores produce germ tubes within a few days upon incubation at 20 °C with ample moisture in the dark without chemical treatment or exogenous nutrient. However, the germ tubes do not branch and germ conidia are not produced until after much longer incubation, and then only sparsely. Light periods of 14 h or more in a 24-h day greatly enhance the germination level but seldom result in germination of more than 50% of the spores. Branching of the germ tubes, germ conidia production, and germination of germ conidia all occur rapidly under long-day conditions. The principal germination interval is between 10 and 30 days under the conditions used and it was estimated that the germination level would stabilize after about 60 days. Variability in germination from plate to plate made with the same spore preparation was from about 25 to 50%.