QUANTITATIVE STUDIES ON THE SURVIVAL OF FUNGI IN FIVE-YEAR-OLD DRIED SOIL CULTURES

Abstract

Of 51 dried soil cultures of fungi isolated from soil, only 12, comprising seven of the 32 genera represented, were viable after five years. Platings, directly from the cultures, of 5-, 50-, and 500-mgm. samples with oxgall-amended potato dextrose agar revealed extreme variations in viability of surviving fungi. Population levels were so high in cultures of Rhizopus nigricans, Aspergillus fumigatus, A. sydowi, and A. ustus that plate counts were not obtained, even when a 5-mgm. sample was apportioned among five plates. Cultures of Chaetomium indicum and of C. spirale contained an estimated population of approximately one and one half million, and 450,000 viable centers per gram, respectively, the highest counts obtained. The next most viable cultures were those of Fusarium oxysporum var. redolens and of Circinella spinosa, but these contained only about 60,000 and 20,000 centers per gram, respectively. Next came Penicillium janthinellum with an estimated 4000 centers per gram. The least viable cultures were those of Penicillium purpurogenum and of two isolates of F. oxysporum whose population level was down to about 100 to 200 viable centers per gram.