Improved biocontrol activity of Trichoderma harzianum by over-expression of the proteinase-encoding gene prb1.

Transformation systems developed for Trichoderma spp. were utilized to improve the biocontrol efficiency of the mycoparasitic fungus Trichoderma harzianum by increasing the copy number of the basic proteinase gene prb1. The transformants were stable and carried from two to ten copies of prb1. High levels of expression of prb1 during fungus-fungus interaction were detected when T. harzianum and Rhizoctonia solani were confronted in vitro. In liquid cultures the proteinase was induced by cell walls of R. solani. Under greenhouse conditions, incorporation of T. harzianum transformants into pathogen-infested soil significantly reduced the disease caused by R. solani in cotton plants.