IN-VITRO INTERACTIONS BETWEEN ALTERNARIA-ALTERNATA, FUSARIUM-EQUISETIAND GLOMUS-MOSSEAE

Germinated spores of the arbuscular mycorrhizas (AM) fungus Glomus mos seae did not affect growth of the saprophytic fungi Alternaria alterna ta and Fusarium equiseti on water agar. Both saprophytic fungi reduced spore germination of G. mosseae independently of pH changes in the me dium. Soluble and volatile substances produced by the saprophytic fung i were involved in the inhibition of spore germination. Although F. eq uiseti inhibited the germination of G. mosseae spores, hyphal growth w as markedly stimulated. The inoculation of maize plants with A, altern ata and F. equiseti simultaneously with spores of G, mosseae significa ntly decreased the percentage of root length colonized by AM fungi, bu t there was no effect on AM colonization when G. mosseae was introduce d before A. alternata and F. equiseti. The number of colony-forming un its (CFU) of A. alternata decreased when G. mosseae was established in the root, but was not affected when both microorganisms were inoculat ed at the same time. The number of CFU of F. equiseti was not affected by the presence of G. mosseae.