Proteolytic activity and antibiotic production by Trichoderma harzianum in relation to pathogenicity to insects

Two strains of Trichoderma harzianum, 101645, an insect pathogen and 206040, used for biological control of fungal plant pathogens were investigated for the production of serine protease, chitinase and antibiotic activity in relation to entomopathogenicity. Both strains produced serine protease with a Mr of 31 kDa and chitinase with a Mr of 44 kDa. Enzymes from both strains had similar characteristics and were produced during the growth phase. Both strains also produced peptaibols active against fungi in late growth and stationary phases which differed in their amino-alcohol content. The peptaibols were insecticidal when fed to larvae of Tenebrio molitor or when applied to the cuticle together with the serine protease. The results suggest that the virulence factors involved in biocontrol are the same as those for insect pathogenicity. This may affect the use of Trichoderma spp. for biocontrol as there may be effects on non-target insect species.