GERMINATION AND HYPHAL GROWTH OF VAM FUNGI DURING AND AFTER STORAGE IN SOIL AT 5 MATRIC POTENTIALS

Four vesicular-arbuscular mycorrhizal (VAM) fungi, Gigaspora margarita Becker & Hall, Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe, Glomus intraradices Schenck & Smith, and Acaulospora longula Spain & Schenck, were studied to characterize the variety of responses of VAM fungi to storage. Spores were stored at 23-degrees-C for up to 4 months in soil at several matric potentials [psi-m], then removed and exposed for 1 month in soil at field capacity to induce germination. Each species studied has a different response to storage duration and moisture availability, reflecting the complexity of the problem of storage of VAM fungi in soil. Net germinability, the difference in percentage germination between that which occurred in storage and germination after the subsequent month at field capacity, was effectively zero for Gi. margarita. Hyphae continued to grow and additional germ tubes were produced upon removal from storage. Gi. margarita spores which produced one germ tube per spore during storage in moist soil subsequently produced less root colonization of Paspalum notatum than spores stored in drier soil. Net germinability of spores of G. intraradices increased with decreasing storage psi-m and was independent of storage duration. Upon removal from storage, preexisting hyphae resumed growth. Net germinability of spores of G. mosseae was inversely proportional to duration of storage and independent of psi-m. Spores which germinated in storage did not resume growth upon removal from storage. Net germinability of A. longula increased with duration of storage and was independent of moisture availability during storage, indicating a dormant period.