Antifungal Potential of Metabolites from Trichoderma sp. Against Colletotrichum falcatum Went Causing Red Rot of Sugarcane

Secondary metabolites produced by the biocontrol fungi Trichoderma have been frequently implicated in the inhibition of diverse plant pathogens in several crops. We carried out laboratory and field studies to assess the antifungal potential of soluble inhibitory metabolites produced by Trichoderma against red rot of sugarcane caused by Colletotrichum falcatum. A total of 33 Trichoderma isolates were selected and assessed for production of soluble inhibitory metabolites against C. falcatum in vitro. Malt extract broth (MEB), potato dextrose broth (PDB) and minimal salts broth were evaluated as growth medium for production of inhibitory metabolites. For most isolates, the highest inhibitory activity was observed with metabolites produced on MEB and lowest when produced on PDB, indicating the importance of growth medium in inhibitory metabolite production. Considerable variability (ranging from 0.7 to 70.6 %) was observed in the inhibitory activity of soluble metabolites of the 33 isolates against C. falcatum with only five isolates showing >40 % inhibition in C. falcatum growth. Field experiments were carried out in two years to evaluate potential of Trichoderma metabolites for management of red rot. Sugarcane setts, pre-inoculated with C. falcatum, were treated with Trichoderma metabolites and planted. Observations on germination failure, settling, tiller and cane mortality due to red rot were recorded regularly. The metabolites of isolates STr-108 and STr-12 showed considerable reduction in red rot incidence (40–55 % reduction over control) in both years. The results indicate that direct application of these metabolites and/or development and application of biopesticides based on them has the potential to provide consistent and effective disease control.