Antagonistic interactions involving trichoderma species

Abstract

An investigation has been made of antagonistic interactions involving Trichoderma species. The problem was studied from two aspects; (1) the effect of fungistasis on spore germination and (2) the production of non-volatile and volatile antibiotics. Sensitivity to soil fungistasis was measured on four parameters of germination (final percentage germination, rate of germination, latent period of germination, and germ tube growth rate) for each of the 20 Trichoderma isolates. Sensitivity varied between the isolates and for any one soil fungistasis did not act equally on the four parameters. There was, however, no apparent consistency for any one parameter to be more affected than another when the results for the different isolates are compared. Positive correlations were however shown to exist between the percentage reduction in the latent period and both the percentage reduction in the final percentage germination and the percentage reduction in the germ tube growth rate. The latent period in the control was directly correlated with the percentage reduction in the final percentage germination. A growth index under fungistatic conditions has been calculated. This has been called the Theoretical Colonization Index and reflects the ability of a spore population to grow under antagonistic conditions in soil. There is a direct correlation between the percentage reduction in the theoretical colonization index and the percentage reduction in performance of each of the other four parameters. Variation in the sporulation media made little significant difference to the sensitivity of T. viride (48) spores to soil fungistasis although considerable variation resulted in the theoretical colonization indices. Bioassay tests with a wide range of fungi indicated that all of the Trichoderma isolates produced non-volatile antibiotics in liquid culture. A large number of biologically active metabolites were produced including a peptide antibiotic similar to the antibiotics alamethicine and suzukacillin. Work with T. viride (48) indicated that the quality and quantity of the active metabolites produced varied with the quality of nutrients in the culture medium and the maturity of the culture. All of the isolates produced volatile antibiotics active against germination of Gliocladium roseum conidia. Volatile antibiotic production by T.Viride (48) growing on different C-sources was found to vary with respect to C-sources was found to vary with respect to C-Source and time; maximum biological activity was found to occur at the same time as production of a ‘coconut’ smell. The nature of these antagonistic interaction is discussed in relation to the ecology of Trichoderma in soil.