Trichoderma spp. NATIVE STRAINS MOLECULAR IDENTIFICATION AND in vitro ANTAGONISTIC EVALUATION OF ROOT PHITOPATHOGENIC FUNGUS OF THE COMMON BEAN (Phaseolus vulgaris L.) cv. MONTCALM

Trichoderma spp. is a fungus of the Ascomycota division with great potential to control diseases in economically important crops. This antagonistic fungus inhibits the growth of phytopathogenic microorganisms, including those responsible for root diseases, such as Rhizoctonia spp. and Fusarium spp. The objective of this study was to identify Trichoderma species and to describe their in vitro antagonistic activity in pathogenic strains of Rhizoctonia solani, F oxysporum, F verticillioides and F solani, with different virulence determined based on pathogenicity tests in bean plants (Phaseolus vulgaris L.) cv. Montcalm. The hypothesis was that the identification and antagonistic description of Trichoderma species against pathogenic fungi defines their biological control efficiency. The experimental design was completely random, with at least three repetitions. The molecular identification of Trichoderma spp. was done through ITS1 and ITS2 regions, separated by the 5.8S ribosomal RNA gene (ITS, Internal Transcribed Spacer). The antagonism was evaluated using the modified cellophane method and dual cultures to estimate the percentage of radial growth inhibition (PRGI). Seven Trichoderma strains identified using molecular techniques showed 95-100 identity to T harzianum and T asperellum. Trichoderma strains showed high antagonistic capacity with 73.1 to 76.4 mean PRGI values in pathogenic strains, suggesting an antibiosis effect (77.6 PRGI) and different hyphal interaction types. Antagonistic strains were statistically similar for pathogen growth and development inhibition; however, T asperellum's antagonistic values were higher than T harzianum's with regard to all pathogenic strains, even R. solani, which was the most aggressive pathogen for cv. Montcalm (mean value: 7.0). The antagonistic effect of Trichoderma strains on phytopathogenic fungi was determined with in vitro tests and corroborated with in vivo bioassays with similar inhibition percentages.