Growth of rhizosphere-competent mutants of Trichoderma harzianum on carbon substrates

Abstract

When the strains of Trichoderma harzianum were grown in Czapek-Dox broth without saccharose with cotton linters, microcrystalline cellulose, wood cellulose, or xylan as a sole source of carbon, the rhizosphere-competent mutants produced significantly higher biomass than the rhizosphere-incompetent wild types. Both mutants and wild types did not readily grow on glucose, galactose, cellobiose, or xylose as sole source of carbon. The mutants, T-95 and T-12B, produced significantly higher biomass when grown on complex carbohydrates with added simple sugars. The wild types did not produce significantly greater biomass when both simple and complex sugars were the carbon sources than when either substrate was used alone. The ability of the mutants to grow more rapidly on complex carbon substrates (typical of those found on root surfaces) than their wild-type parents, and to increase biomass when simple sugars were added along with the cellulose substrate could be of ecological significance and a characteristic of rhizosphere competence.