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Ecology and Epidemiology

Competitive Saprophytic Ability and Cellulolytic Activity of Rhizosphere-Competent Mutants of Trichoderma harzianum. Jaleed S. Ahmad, Research associate, Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523; Ralph Baker, Professor, Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523. Phytopathology 77:358-362. Accepted for publication 25 July 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-358.

Competitive saprophytic ability (CSA) of strains of Trichoderma spp. was determined by the modified Cambridge method (sensu Garrett). Two rhizosphere-competent mutants of T. harzianum (T-95 and T-12B) had higher CSA indices than four rhizosphere-incompetent Trichoderma spp. and strains. CSA was directly correlated with rhizosphere competence (RC). When the strains were grown for 6 days on Czapek-Dox broth with cellobiose, carboxymethyl cellulose, or cotton linters as sole sources of carbon, mutants produced more cellulase than the wild types. The amount of cellulase produced by these strains was directly correlated with CSA and RC, RC of the mutants, therefore, can be at least partially explained by their capacity to utilize cellulose substrates associated with the root.