SPORE GERMINATION AND HYPHAL GROWTH OF ARBUSCULAR MYCORRHIZAL FUNGI IN RELATION TO SOIL ALUMINUM SATURATION

Several arbuscular mycorrhizal fungi were evaluated for aluminum tolerance based on spore germination and hyphal growth in soils with 6%, 27%, and 100% aluminum saturation. There were interspecific as well as intraspecific variations in aluminum tolerance. Most species of Gigaspora showed high tolerance. Often, spore germination was not affected by aluminum saturation as in Gi. margarita (International Culture Collection of VA Mycorrhizal Fungi isolate GMRG 444) or was even increased as in Gi. albida (GABD 185). Similarly, hyphal growth of Gi. margarita (GMRG 444) and Gi. gigantea (GGGT 663) was not affected, while that of Gi. gigantea (GGGT 109) was increased by increasing aluminum saturation. Aluminum did not affect the spore germination of most Scutellospora species but did reduce their hyphal growth. Glomus species proved extremely sensitive to aluminum except Gl. manihot (LMNH 980) which showed consistently high germination in all the aluminum-saturated soils. Aluminum tolerance may be an important factor in the selection of arbuscular mycorrhizal fungi for acid mineral soils.