GENETIC IMPROVEMENT OF ANTAGONISTIC FUNGI AND THEIR ABILITY TO INDUCE SYSTEMIC DISEASE RESISTANCE IN THE PLANT

The interaction between Trichoderma spp., other soil or leafmicrobes (including phytopathogens) and the plant is much morecomplex than it was thought. These beneficial fungi seem to havethe remarkable ability to function at the same time both as microbialantagonists and plant symbionts, by using a variety of molecularfactors and specialized structures. For example, seed treatmentswith various Trichoderma strains provide increased resistanceto infection on the leaves by Botrytis cinerea. Recent understandingof the mechanisms of fungal antagonism at the molecularlevel is providing new tools to genetically improve the performanceof biocontrol agents. A number of antifungal compoundshave been identified and their specific role assessed by gene disruption.Further, a few promoters induced during mycoparasitismand biocontrol have been cloned and characterized, andthey can be used to express in an inducible manner foreign genesthat may augment biocontrol ability. For instance, we have expressedin T. atroviride a gene of Aspergillus nidulans encodingfor a glucose oxidase under a biocontrol-related promoter, andhave obtained mutants more powerful than the wild type both inpathogen biocontrol and induction of systemic disease resistancein the plant.