Bacterial wilt induced changes in nutrient distribution and biomass and the effect of acibenzolar-S-methyl on bacterial wilt in tomato

Bacterial wilt (BW) caused by the bacterial pathogen Ralstonia solanacearum is one of the most important diseases of tomatoes in the southeastern United States due to its destructive nature, wide host range, and geographical distribution. Acibenzolar-S-methyl (ASM, Actigard 50 WG), is a systemic acquired resistance inducer. Greenhouse experiments were carried out to study the physiological changes in tomato during BW induction. Tomato plants were treated with ASM by foliar spray (25 μg ml−1) and soil drench (12.5 μg ml−1) and inoculated with different concentrations of pathogen. Plants uninoculated or untreated with ASM were used as controls. BW incidence was recorded weekly after inoculation and quantified as a percentage of plants wilted. Measurements of height, biomass, and shoot nutrient concentrations were made at 7, 14, 21, and 28 d after inoculation. Height and shoot biomass decreased rapidly in plants not treated with ASM but inoculated with low or high concentrations of the pathogen. Nutrient concentrations such as Ca, B, and P declined in the leaves of inoculated plants when compared with the untreated control. Application of ASM significantly reduced BW incidence when plants were inoculated with lower concentrations of R. solanacearum. The results suggest that BW could be significantly reduced by ASM under low BW inoculum conditions. Furthermore, BW resulted in a reduction of concentrations of Ca, B, and P in tomato leaves. To our knowledge, this is the first report on the distribution of several macro- and micro-nutrients in tomato as related to BW.