Changes in the Incidence of VA Mycorrhizal Fungi with Changes in Ecosystems

Abstract Root-soil samples were collected from native cerrado vegetation and adjacent agricultural crops in cultivated soils. Samples were processed and spores of VA mycorrhizal fungi were counted and identified. The frequency and the relative numbers of spores for each species varied with location but the average number of spores per kg of soil was greater in cultivated soils than native soils. In native soils, 18 species of VA mycorrhizal fungi predominated but in agroecosystems the number of predominant species was less. Although total spore numbers were higher in agroecosystems, a greater diversity of predominant species of VA mycorrhizal fungi occurred in natural ecosystems. The possible effect of this reduction in predominant species with change from a native to an agroecosystem on the incidence of decline-type diseases is discussed.