In vitro germination of Entomophthora egressa resting spores

Abstract

The resting spores of Entomophthora egressa MacLeod and Tyrrell germinated to produce a single germ tube, which in turn, produced a solitary, terminal germ conidium. The level of resting spore germination obtained in shaken, liquid, steam-sterilized media after 12 h of incubation at pH 7.5 was 93%. The effect of pH on resting spore germination in filter-sterilized media was investigated; in the range pH 4.5 to 9.5, pH 8.5 and 9.5 were optimal (100% germination after 96 h). No germination occurred at pH 4.5 to 6.5 before 96 h. At values greater than pH 6.5, the proportion of resting spores which germinated to form a single germ tube with a solitary germ conidium decreased, and the resting spores increasingly germinated by forming one to five hyphae. At high pH values (pH 7.5 to 9.5) septa occurred in the hyphae after 120 h of incubation. This latter phenomenon may have been correlated with the occurrence of hyphal bodies in shaken media at high pH (pH 8.5). The germination of resting spores to form hyphae at high pH levels may indicate the presence of a mechanism for infection via the gut.