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

Relations between spores and propagules of a mycorrhizal fungal commun ity were studied in a tall fescue pasture which was plowed in late fal l. then either reseeded in tall fescue or planted to tobacco the follo wing spring. Soilborne populations of viable spores, isolated by wet-s ieving, or propagules. determined by bioassay, were measured throughou t a growing season and the following spring. Populations of spores of all species declined at least 7-fold from spring through mid-summer, t hen rose in the fall to densities not different from those in the spri ng. Populations of spores declined to some extent over-winter. Populat ions of propagules, however, were relatively constant. Spore and propa gule 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 ea rly spring. propagules are primarily spores: whereas in spring, spores germinate, and propagules are primarily mycelia until sporulation occ urs in the fall.