Strain improvement of predacious fungi: In vitro screening of mutant strains for benzimidazole tolerance

The effect of benzimidazole drugs (carbendazim, triclabendazole and albendazole) at different concentrations (0.5, 2.5, 4.5 ppm) on in vitro growth profiles of the mutant strains of Duddingtonia flagrans and Verticillium chlamydosporium were studied compared to those of control (wild isolate). The study revealed that carbendazim had a total inhibitory effect on wild isolate and both the mutant strains of D. flagrans and V. chlamydosporium, while triclabendazole has no inhibitory effect. Albendazole exerted total inhibitory effect on wild strains of both D. flagrans and V. chlamydosporium. While growth of ethyl methane sulphonate mutants of D. flagrans (DF-EMS) and V. chlamydosporium (VC-EMS) were significantly inhibited in presence of albendazole, albendazole mutants of D. flagrans (DF-ABZ) and V. chlamydosporium (VC-ABZ) could able to withstand the presence of albendazole in culture media and appeared to be albendazole resistant. Triclabendazole did not appear to have significant antimycotic property under in vitro conditions on both the fungal groups and albendazole displayed antimycotic effect on both the nematode-trapping and egg parasitic fungus, however, mutant strains exhibited some degree of albendazole tolerance. Thus, the use of carbendazim as fungicide in agricultural crops should not coincide with application of nematodetrapping and egg parasitic fungi as biological control agents.