EFFECT OF BORON NUTRITION ON RESISTANCE RESPONSE OF TOMATO AGAINST BACTERIAL WILT CAUSED BY RALSTONIA SOLANACEARUM.

This study investigated the effect of boron nutrient on tomato bacterial wilt caused by Ralstonia solanacearum and the regulation mechanisms. Plants, cultured in nutrient solution and treated with three concentrations of B (0.05, 0.50 and 2.50 mg l-1), were inoculated with R. solanacearum by the method of root dip. Severity of disease development, plant nutrient uptake, hydrogen peroxide (H2O2) activity, enzymes like peroxidase (POD, EC 1.11.1.7), polyphenol oxidase (PPO, EC 1.10.3.2) activities in tomato leaves were analyzed. Disease severity of low, medium and high B treatments were 95.2%, 72.6% and 63.4% respectively. There was no significant difference in plant dry weight, indicating no B toxic or deficiency phenomenon in all treatments. Tomato plants absorbed significantly more Ca and B with the level of B in the nutrient solution increased. In addition, H2O2 level in high B treatment rose faster and reached a higher peak with 11.94 μM gFW-1 (96.7% greater than low B plants). The activities of POD and PPO also have a greater increase in high B treatment with 97.12 U gFW-1 and 94.00 U gFW-1 compared to 39.16 U gFW-1 and 70.51 U gFW-1 in low B treatment. These results suggested that the regulation mechanism of B was to increase the Ca and B concentration, improve the rate and the amount of H2O2 accumulation, and increase the activities of POD and PPO in tomato. [ABSTRACT FROM AUTHOR]