First evidence of Trichoderma longibrachiatum as an effective antagonist against Rigidoporus microporus

Rigidoporus microporus, the causal agent of white root rot, remains a persistent threat in tropical plantations, and sustainable control methods are needed. In this study, fifty Trichoderma isolates collected in Japan were first screened for antagonistic activity against a Japanese R. microporus isolate. The top 20% (ten isolates) showing strong inhibition were subjected to a second evaluation in which the pathogen had already established substantial growth, resulting in the selection of six robust strains. Molecular identification (ITS+TEF) revealed three species: T. longibrachiatum, T. asperellum, and T. lixii. Representative isolates of each species were further tested against three additional R. microporus isolates from Indonesia. Among all strains examined, WT2415 (T. longibrachiatum) consistently exhibited the strongest inhibitory activity across all pathogen isolates. These results provide the first evidence that T. longibrachiatum can act as an effective antagonist against R. microporus, highlighting its potential as a biological control agent.