Rhizosphere competence of benomyl-tolerant mutants of Trichoderma spp.

Abstract

Two strains of Trichoderma harzianum and one each of T. koningii, T. polysporum, and T. viride were mutated for tolerance to the fungicide benomyl. Rhizosphere competence index of several mutants of each strain and species was determined by the rhizosphere competence assay. Most of the mutants and not their wild type parents were rhizosphere competent. When the strains and species were grown in Czapek–Dox broth for 6 days with cellulose as sole carbon source, the mutants produced significantly higher dry weight than their parent wild types. Neither the mutants nor the wild types produced biomass in glucose comparable to that in cellulose. Evidence indicates that Trichoderma spp. were induced by mutation to increase their linear growth rate and to become rhizosphere competent. Tolerance to benomyl does not seem to be a necessary attribute of rhizosphere competence.