In vitro-In vivo efficacy of Trichoderma asperellum and Trichoderma virens against Ganoderma boninense in oil palm...

Oil palm (Elaeis guineensis Jacq.) is a strategic commodity in tropical regions, serving as a major source of vegetable oil. However, its productivity is threatened by basal stem rot (BSR) associated with Ganoderma spp., which can cause severe yield losses. This study evaluated the biocontrol potential of Trichoderma asperellum and Trichoderma virens against a pathogenic Ganoderma isolate using morphological and molecular identification, in vitro dual-culture assays, and greenhouse bioassays. Molecular analysis indicated that isolate UBGb.1 was closely related to G. boninense (99.88% similarity, based on Tef1α sequencing), while UBPg.3 and EXPg.2 were identified as T. asperellum and T. virens (100% similarity), respectively. In vitro, T. asperellum inhibited Ganoderma mycelial growth by 51.14%, outperforming T. virens (35.90%). In vivo assays showed that increasing pathogen inoculum dose increased disease development in oil palm seedlings. Under beneficial microbe application, T. asperellum (140 g pot⁻¹) suppressed visible disease symptoms for 42 d after inoculation (DAI) (DSI = 0%), whereas the consortium treatment resulted in higher disease severity than the single-strain treatment (DSI 10.88% at 42 DAI). Overall, T. asperellum consistently showed superior performance compared with T. virens. These results suggest that nursery-scale biocontrol efficacy depends on strain stability and consistent antifungal activity, and that incompatibility between strains may reduce performance due to physiological competition.