Biocontrol of Fusarium Wilt in Okra (Abelmoschus esculentus) Using Glomus mosseae and Bradyrhizobium japonicum

Introduction: Fusarium wilt, caused by the soil-borne pathogen Fusarium oxysporum, is a major constraint to okra (Abelmoschus esculentus (L.) Moench) production, leading to significant yield losses. Due to the environmental and health concerns associated with chemical control, this study investigated the efficacy of biological control agents, specifically the separate and combined inoculations of the arbuscular mycorrhizal (AM) fungus Glomus mosseae and the bacterium Bradyrhizobium japonicum, in managing Fusarium wilt and enhancing okra growth.

Methods: A greenhouse experiment was conducted using a randomized complete block design with 13 treatments and three replications. Okra seedlings were subjected to various inoculation regimes with G. mosseae, B. japonicum, and F. oxysporum, applied either singly, simultaneously, or sequentially. Key growth parameters, including plant height, stem girth, leaf number, and leaf surface area, were measured over five weeks. Disease severity was assessed based on visual symptoms. Data were analyzed using Analysis of Variance (ANOVA).

Results: Plants inoculated with F. oxysporum alone exhibited severe wilting, chlorosis, necrosis, and stunted growth. In contrast, inoculation with G. mosseae alone significantly enhanced all growth parameters and suppressed disease symptoms. The suppressive effect on the pathogen was most pronounced in treatments involving dual inoculation of G. mosseae and B. japonicum, particularly when applied before the pathogen. B. japonicum alone could not effectively suppress the pathogen. The susceptibility of okra to F. oxysporum was found to be age-mediated, with the most significant growth changes occurring between the second and fourth weeks after inoculation.

Conclusion: The study demonstrates that Glomus mosseae is effective in suppressing Fusarium wilt and promoting okra growth. For Bradyrhizobium japonicum to be an effective biocontrol agent, it must be co-inoculated with G. mosseae. These findings highlight the potential of using these biological agents, especially in combination, as a sustainable strategy for managing Fusarium wilt in okra cultivation.