BIOCONTROL CAPACITY OF NATIVE ISOLATES OF Trichoderma sp. AGAINST THE PHYTOPATHOGENIC FUNGUS Alternaria alternata ISOLATED FROM YERBA MATE (Ilex paraguariensis Saint Hil.)

Phytopathogenic fungi attack many agricultural crops such as yerba mate (Ilex paraguariensis Saint Hil.). An innovative alternative for pest control is the use of biocontrol fungi of Trichoderma genus. The objectives of the present work were to isolate the fungal agents that cause foliar lesions in yerba mate, and to evaluate the antagonistic capacity of native Trichoderma sp. isolates against pathogens in this crop. From diseased plant-tissues, a phytopathogenic fungus belonging to Alternaria alternata species was isolated and identified morphologically and molecularly. Pathogenicity assays were done on yerba mate plants in triplicate. Superficial mechanical lesions were made on them and the phytopathogenic isolation obtained (conidia and mycelium) was inoculated to evaluate their phytopathogenic capacity. New dual culture methods were determined to evaluate in vitro antagonism of Trichoderma. The in vitro biocontrol capacity of 30 Trichoderma isolates was evaluated against the phytopathogenic isolation obtained. As a positive control, a strain isolated from a commercial fungicide product based on T. harzianum was used. It was determined that 18 of the 30 isolates of Trichoderma inhibited the growth of the phytopathogen A. alternata by more than 50%, and presented statistically significant differences with respect to the positive control. These results confirm the effectiveness of using native biocontrol isolates adapted to the climatic and soil conditions where the phytopathogenic microorganisms are found.