Trichoderma sp. is a promising biocontrol agent against phytopathogens that cause significant yield losses in various crops. The following study aimed to identify the Trichoderma spp. isolates through morphological and molecular characterizations and to select the most potential Trichoderma isolates antagonistic to the fungi species Colletotrichum sp. and Rhizoctonia solani. Trichoderma spp. colonies exhibited a flat elevation with a central regular edge, central yellow to green with white edges, and the highest degree of branching and pyramid-shaped conidiophores. The 17 isolates belonged to Trichoderma asperellum (13 isolates), T. gamsii (one isolate), T. harzianum (two isolates), and T. koningiopsis (one isolate). By dual culture assays, T. koningiopsis TR3 and T. asperellum Pan23.1 had the higher growth inhibition than others against the phytopathogen Colletotrichum, accounting for 75.86% and 82.76%, respectively. T. asperellum Kun4, T. asperellum Pan23.2, and T. koningiopsis TR3 demonstrated their supreme growth inhibition against the phytopathogen Rhizoctonia (85.00%, 87.50%, and 92.50%, respectively). The preliminary screening of isolates T. asperellum (Pan23.1, Pan23.2, and Kun4) and T. koningiopsis TR3 confirmed their ability as potential biocontrol agents. Therefore, further studies are essential to explore these four isolates as effective biocontrol agents for controlling the phytopathogens Colletotrichum sp. and Rhizoctonia solani.

Keywords: Trichoderma spp., biocontrol agent, antagonism, Colletotrichum sp., Rhizoctonia sp., growth inhibition, crop losses, ITS

Key findings: Based on morphological and molecular characteristics, the 17 tested isolates acquired from this study attained grouping in the same cluster identified as Trichoderma asperellum, T. gamsii, T. harzianum, and T. koningiopsis. Dual culture tests demonstrated that T. koningiopsis TR3 and T. asperellum Pan23.1 had the highest growth inhibition against Colletotrichum. The T. asperellum Kun4 and Pan23.2 and T. koningiopsis TR3 exhibited the greatest antagonism against the phytopathogen Rhizoctonia.