Abstract
Ralstonia solanacearum (Rs) race 3 biovar 2, the cause of bacterial wilt, is an economically important pathogen in tropical, subtropical and temperate regions of the world. We investigated the induced defence responses against tomato bacterial wilt by the application of acibenzolar-S-methyl (ASM) and Pseudomonas fluorescens (Pf2) alone or in combination. Seedling treatments of tomato plants with either Pf2 or ASM significantly reduced disease severity of bacterial wilt (58 and 56% disease reduction, respectively) of tomato plants. The highest disease reduction (72%) resulted from a combined application of both Pf2 and ASM. The application of ASM alone increased seedlings biomass relative to infected control with 64.3%. Changes in the activities of polyphenol oxidase (PPO), beta-glucosidase (beta-GL) and peroxidase (PO) in tomato after the application of ASM and Pf2 and inoculation with Rs were studied. Significant changes (P = 0.05) in the activities of PPO, beta-GL and PO were found. These results indicate that the future integrated disease management programmes against tomato bacterial wilt may be enhanced by including foliar sprays and soil drench of ASM and P. fluorescens. This is the first report of the use of both ASM and Pf2 to control the tomato bacterial wilt disease under field conditions.