Aims: This study was designed to investigate the effects of 10 heavy metals on the in vitro activities of beta-glucosidase, cellobiohydrolase, beta-xylosidase and endoxylanase enzymes for six strains of Trichoderma, and to isolate and characterize heavy metal-resistant mutants.
Methods and results: At a concentration of 1 mmol, only mercury showed significant inhibitory effects on the in vitro enzyme activities; in all other cases, the enzymes remained active. A total of 177 heavy metal-resistant mutants were isolated and tested for cross-resistance to other heavy metals. Some mutants were effective antagonists of Fusarium, Pythium and Rhizoctonia strains, even on media containing the respective heavy metals.
Conclusion: Trichoderma strains could be developed as biocontrol agents that are effective against plant pathogenic fungi, even under heavy metal stress.
Significance and impact of the study: Trichoderma mutants resistant to heavy metals might be of value for use with heavy metal-containing pesticides, as part of an integrated plant protection system.