Damping-off caused by Pythium aphanidermatum is a serious threat to tomato seedlings and significantly hampers both germination and plant vigour. For effective management of plant disease, Trichoderma spp are used as potential biocontrol agents against phytopathogens. The present study aimed to evaluate the antagonistic efficacy of native Trichoderma spp. isolated from rhizosphere soils across Tamil Nadu was against P. aphanidermatum. A total of 19 Trichoderma isolates were morphologically characterized and screened under in vitro conditions using quadrium and dual plate assays. Among the isolates tested, the highest mycelial growth inhibition was noticed in isolates T9 (74.81 per cent) and T18 (67.41 per cent), which showed a significant difference between the other treatments tested. The isolate T18 showed hyperparasitic activity against P. aphanidermatum, characterized by hyphal coiling and enzymatic degradation. These findings highlight the potential of specific Trichoderma strains as eco-friendly biocontrol agents for managing damping-off in tomato nurseries, offering an effective alternative to chemical fungicides

Trichoderma, Pythium aphanidermatum, damping-off, tomato, biocontrol, dual culture, hyper parasitism

The present study clearly showed that Pythium aphanidermatum is a major cause of damping-off disease in tomato seedlings, leading to severe losses during early growth stages. The pathogen was identified based on its typical cultural and microscopic features. Among the 19 native Trichoderma isolates tested, a few showed strong antagonistic activity against the pathogen, especially isolates T9 and T18, which significantly suppressed its growth in dual culture assays. Isolate T18 also showed hyperparasite behaviour, indicating its potential as an effective biocontrol agent. These findings suggest that certain native Trichoderma strains could be developed into eco-friendly alternatives to chemical fungicides for managing damping-off in tomato

Gokul R.V., Akshaya S.B., Karpagavalli S. and Melvin Joe M. (2025). Antagonistic Activity of Trichoderma spp. Against Pythium aphanidermatum causing Damping-off in Tomato. Biological Forum, 17(8): 67-74