PLANT GROWTH AND ISR PROMOTION BY TRICHODERMA HARZIANUM T22

Trichoderma harzianum T22, a fungal antagonist, is one of themost widely used active ingredients in commercial bio-fungicidesand bio-fertilizers. It has not only mycoparasitic activity, but canalso activate extensive metabolic changes in treated plants, resultingin a systemic resistance to a pathogen attack, thus indirectlyaltering plant-pathogen interactions. By analyzing the T.harzianum T22 “secretome” a few key “effectors” involved in Trichoderma-plant cross-talk were identified. One of these effectorssecreted was a class II hydrophobin HYTRA1. This protein wastested for its antimicrobial activity and its ability to induce a defenceresponse in tomato plants. In in vitro and in vivo assays,HYTRA1 directly inhibited pathogen development. In tomatoplants, depending upon the concentration, it induced a multiplicityof effects. HYTRA1 activated oxidative burst, the antioxidantsystem, and ISR with the accumulation of defence-related compoundsimportant in plant defence. Further physiological effectsincluded the induction of de novo rhizogenesis, and an epinasticphenotype in HYTRA1-transformed tomato. The involvement ofHYTRA1 in the T. harzianum molecular crosstalk with the plantwas confirmed when HYTRA1 disruptants proved unable to induceroot growth promotion and ISR in tomato.