Antagonistic activity of Trichoderma fungi isolated from the soil

Approximately 200 soil samples were collected from pastures, forests, and cultivated fields in Ulaanbaatar city, as well as provinces such as Tuv, Selenge, and Bulgan in 2018. These samples were diluted using Koch's serial dilution method and cultured on Potato Dextrose Agar (PDA) medium supplemented with Streptomycin (0.03 g). Pure cultures of Trichoderma were selected based on their morphological characteristics after 7–10 days of incubation at 25°C. The antagonistic activity of Trichoderma against various fungal pathogens was determined using the dual culture method. For the identification of Trichoderma species, DNA was extracted using CTAB buffer, and the ITS1 and ITS4 rDNA regions were PCR amplified, purified, and sequenced at Macrogenes, in South Korea. The sequences were compared to those in the NCBI GenBank database to establish phylogenetic relationships. Trichoderma was detected in 11 samples out of the approximately 200 soil samples. Eleven pure cultures of Trichoderma fungi were isolated and identified as T. harzianum, T. citrinoviride, T. sinuosum, and T. virens based on molecular biology and sequence analysis. When tested for antagonistic activity against A. alternata, Cladosporium fulvum, and F. oxysporum pathogens, all 11 pure cultures of Trichoderma showed more than 54% activity. On average, the T. citrinoviride 31/4 pure culture showed 67.8% antagonistic activity, while the T. harzianum 186/4 pure culture showed 70.5% antagonistic activity.