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ABSTRACT
The genus Trichoderma comprises various fungal strains that can act as biological control agents against a large diversity of plant pathogens. A number of commercial products are available but the diversity of plant pathogens, and their increased resistance to the current control products (chemical or biological products) determined the search of new strains, potentially useful for biological control. New strains of Trichoderma spp. were isolated from Romanian soils and their antagonistic activity against Phytium spp and Rhizoctonia spp. was examined. The in vitro biocontrol activity of Trichoderma spp., as well as of other antagonistic fungi (Penicillium chrysogenum Gliocladium roseum and Eppicoccum purpurescens) on the plant pathogens was increased in the presence of FeCl3. The molecular analysis realized by ITS-RFLP and PCR with specific primers allow the confirmation of previous taxonomic determination of T.harzianum and T.viride. However, an increased intraspecific molecular polymorphism was observed using several arbitrary primers (RAPD analysis). The interactions between fungal strains (plant pathogens and antagonistic strains) were also examined, in order to determine the mechanism of action of the antifungal strains. It was observed that all of the Trichoderma strains were able to produce large amount of hydrolytic enzymes (chitinase, cellulases and proteases) and to act as mycoparasites for pathogens. The involvement of fungal lectins in the interactions was also examined. Fungal extracts obtained from the best antagonists were tested for the induction of plant (soybean) resistance against pathogens. Higher levels of plant enzymes PAL, POX and chitinase were observed, and correlated with an increased resistance to artificial infection. The results obtained could be used in further experiments to establish new approaches of “rplant immunization” with microbial products.