Biological Control of Fusarium Wilt in Corchorus olitorius Using Indigenous Fungal Antagonists: Integrated In Vitro and Screenhouse Evaluation

Fusarium wilt caused by Fusarium oxysporum is a major constraint to the production of Corchorus olitorius in tropical agroecosystems, yet information on the effectiveness of fungal biocontrol agents in this crop under West African conditions remains limited. This study evaluated the antagonistic potential of selected indigenous soil fungi ( Trichoderma harzianum , Aspergillus niger , and Aspergillus flavus ) against F. oxysporum using integrated in vitro and screenhouse experiments. Antagonistic activity was assessed using dual culture assays, while a factorial completely randomised design was employed to evaluate disease incidence (DI), disease severity index (DSI), and plant growth responses at inoculum concentrations of 1 × 10 ⁸ and 1 × 10 ¹⁰ conidia mL ^-1 . All antagonists significantly (P ≤ 0.05) inhibited pathogen growth in vitro, with T. harzianum showing the highest inhibition (68%). Under screenhouse conditions, treatments differed significantly in DI and DSI, with T. harzianum at 1 × 10 ¹⁰ conidia mL ^-1 consistently recording the lowest disease levels. Disease severity showed a strong negative correlation with plant height (r = -0.957, P ≤ 0.001), and regression analysis indicated that DSI accounted for 91.6% of the variation in plant height. In addition to disease suppression, T. harzianum significantly improved plant growth parameters, including plant height, stem girth, and leaf development, confirming its dual role as a biocontrol and plant growth-promoting agent. Aspergillus niger exhibited moderate effects, whereas A. flavus showed comparatively lower efficacy. These findings demonstrate the potential of T. harzianum for sustainable management strategies for Fusarium wilt in Corchorus olitorius , although further field validation and molecular characterisation are required for wider application.