POPULATIONS OF SPORES AND PROPAGULES OF MYCORRHIZAL FUNGI IN RELATION TO THE LIFE-CYCLES OF TALL FESCUE AND TOBACCO

Relations between spores and propagules of a mycorrhizal fungal community were studied in a tall fescue pasture which was plowed in late fall. then either reseeded in tall fescue or planted to tobacco the following spring. Soilborne populations of viable spores, isolated by wet-sieving, or propagules. determined by bioassay, were measured throughout a growing season and the following spring. Populations of spores of all species declined at least 7-fold from spring through mid-summer, then rose in the fall to densities not different from those in the spring. Populations of spores declined to some extent over-winter. Populations of propagules, however, were relatively constant. Spore and propagule population dynamics were similar for fescue and tobacco, although the phenologies of the two plants differ. Sporulation was not related to reproduction of fescue. These data suggest that from fall until early spring. propagules are primarily spores: whereas in spring, spores germinate, and propagules are primarily mycelia until sporulation occurs in the fall.