Protease over-production in the presence of copper by a Trichoderma harzianum strain with biocontrol potential

The effect of copper on the production of extracellular trypsin-like proteases of Trichoderma harzianum T66 was examined. Trypsin-like protease enzyme activities were significantly enhanced in the presence of copper ion. It was demonstrated that instead of raising the activity of previously produced enzymes, copper ions are able to induce the secretion of extracellular trypsin-like proteases. Supernatants of control and CuSO4-containing cultures with the highest enzyme activities were separated by gel filtration chromatography and enzyme activities were measured in the fractions collected. It turned out that in the presence of copper certain extracellular trypsin-like protease izoenzymes are produced in a larger degree both under inductive and non-inductive conditions. Our results suggest that the antagonistic abilities of Trichoderma strains could be enhanced by adding certain sublethal amounts of CuSO4. Consequently, an appropriate level of crop protection could be ensured by the application of reduced amounts of copper-containing fungicides in combination with biocontrol Trichoderma strains within the frames of integrated pest management.