INFLUENCE OF SOIL EXTRACTS ON GERMINATION OF CONIDIA OF FUNGI BEAUVERIA BASSIANA AND PAECILOMYCES FARINOSUS

Unsterilized aqueous extracts of soil inhibited germination of conidia and germtube growth in the fungi Beauveria bassiana and Paecilomyces farinosus. Extracts of the deepest layer of soil were less inhibiting than extracts of overlying layers of humus-rich soil and partially decomposed leaves. The inhibitory properties were reduced by autoclaving and by filtering the extracts. One percent dextrose ( w w) and an aqueous extract of the silk of Bombyx mori cocoon increased the percentage germination and germ-tube growth in both fungi, and also reduced the inhibitory effects of the soil extracts on B. bassiana conidia. Though these amendments improved germination of P. farinosus conidia in the extract of the deepest layer of soil, they failed to improve appreciably their germination in extracts of the upper soil layers. Inhibitors in the soil were found to be capable of diffusing through agar and to be fungistatic rather than fungicidal. © 1969.