Development of UV-induced Carbendazim-resistant mutants of Trichoderma harzianum for integrated control of damping-off disease of cotton caused by Rhizoctonia solani

The treatment of seeds with Trichoderma harzianum has been used successfully to control damping-off of cotton and other crops. However, T. harzianum is very sensitive to carbendazim which is often used as a seed-dressing fungicide for the control of internally seed-borne fungal pathogens. Hence in the present study, carbendazim-resistant mutants of T. harzianum were developed through UV-irradiation. These mutants grew well in PDA medium containing the carbendazim even at 100 μg/ml. Sustained production of cellulase and chitinase by these mutants in the presence of carbendazim in the growth medium was observed. These mutants established well in the rhizosphere of cotton plants. Seed treatment with carbendazim followed by application of carbendazim-resistant mutants of T harzianum resulted in better plant stand, plant biomass and less damping-off disease caused by R. solani in both greenhouse and field conditions.