Efficacy of microbial antagonists in the management of bacterial wilt of field-grown tomato

Abstract

Bacterial wilt caused by Ralstonia solanacearum can cause up to 100% yield loss in tomato production and has compelled many farmers to abandon previous productive farms. Consequently, the absence of an effective control method demands an intensive such for a functional management option. The study was carried out to evaluate the efficacy of microbial antagonists in managing bacterial wilt under field conditions. The experiment was laid down under Randomized Complete Block Design and four replicates maintained for each treatment. Antagonistic strains of locally isolated Trichoderma hamatum, T. atroviride, T. harzianum, Bacillus subtilis, Serratia spp., and Acinetobacter spp. were assessed. Commercial formulations of T. viride (Bio Cure F®) and Pseudomonas fluorescence (Bio Cure B®) were included as standard checks. Treatment application was initiated at transplanting by drenching the rhizosphere with 50 ml of the inoculum. Application was repeated every two weeks until tenth week after transplanting. Data was collected on plant stand count, disease incidence, disease severity, plant height, plant biomass, and fruit weight. Trichoderma hamatum was the most effective in experiment 1, reducing crop mortality, incidence and AUDPC by up to 51.7%, 49.3% and 58.2%, respectively. It also exhibited the highest percentage yield increase by up to 196.4% compared to the untreated control. In contrast, B. subtilis showed superior disease suppression in experiment 2, reducing crop mortality, incidence and AUDPC by up to 44.6%, 48.5% and 51.0%, respectively. It also increased biomass by approximately 62.0% in both experiments. It was closely followed by Serratia spp., which also gave the highest yield output in experiment 2 of up to 233.0%. These findings suggest that novel antagonistic strains T. hamatum and B. subtilis presents unique opportunities for exploiting local microbial resources as biocontrol products. These products can be incorporated as part of an integrated bacterial wilt management program in farms where production is significantly affected by the disease.