Screening of antimicrobial activities in Trichoderma isolates representing three trichoderma sections.

Methanol extracts from 24 Trichoderma isolates, selected as biocontrol agents and representating different species and genotypes from three of the four taxonomic sections of this genus (T. sect. Trichoderma, T. sect. Pachybasium and T. sect. Longibrachiatum) were screened for antibacterial, anti-yeast and antifungal activities against a panel of seven bacteria, seven yeasts and six filamentous fungi previously used in similar studies. Two different growth media were tested (potato dextrose broth and CYS80), and all isolates included in the antimicrobial tests showed at least one inhibitory activity against one of the target microorganisms in one of the two culture media. No statistically significant differences were detected in the number of active strains between the two culture media, but the highest number of inhibitory strains against bacteria and fungi were found in strains from Trichoderma sect. Pachybasium, whereas strains from T. sect. Longibrachiatum showed the highest anti-yeast values. In all cases, a correlation was found between the strains that were active against yeasts and fungi. However, some degree of variability was detected for strains within the same taxonomic section. In general terms, strains from T. asperellum (mainly in CYS80 medium), and T. longibrachiatum gave the best non-enzymatic antimicrobial profiles.