Biocontrol Efficacy of Trichoderma sp. THR3 Against Sclerotium rolfsii SCO1 Causing Damping-Off in Durian Seedlings

Damping-off disease threatens durian seedling production and can facilitate pathogen dissemination during transplanting. This study evaluated the biocontrol potential of Trichoderma sp. THR3 against Sclerotium rolfsii associated with damping-off of durian seedlings. Three isolates, SCO1, SCO2, and SCO3, were obtained from symptomatic seedlings and identified using morphological characteristics and internal transcribed spacer sequence analysis. In pathogenicity tests conducted on two-month-old durian seedlings, SCO1 was the most aggressive isolate and produced 100% disease incidence. In dual culture, Trichoderma sp. THR3 inhibited the mycelial growth of SCO1 by 88.7% at 7 days after inoculation. In the in planta experiment using one-year-old grafted durian plants, treatment with Trichoderma sp. THR3 resulted in a 50% numerical reduction in final disease severity caused by S. rolfsii SCO1 relative to the pathogen-inoculated control at 9 days after inoculation (DAI). Disease incidence was numerically lower in THR3-treated plants (60%) than in the pathogen-inoculated control (100%); however, this difference was not statistically significant (p > 0.05). These findings indicate the potential of Trichoderma sp. THR3 as a candidate biological control agent against S. rolfsii SCO1 in grafted durian nursery plants, although further replicated experiments are needed to confirm its efficacy under nursery and field conditions.