Elicitor-Induced Defense Responses in Tomato Plants Against Xanthomonas gardneri

Resistance inducers have been focused on promising environment-friendly options to chemical pesticides. In the present study, eleven potential resistance inducers were investigated toevaluate their efficacy in mitigating the adverse impacts of bacterial spot disease in tomatoplants. Results revealed that catalase activity and hydrogen peroxide content were sustantiallydifferent in inoculated and non-inoculated plants irrespective of the resistance inducer used.The mean concentration of H2O2 in the inoculated plants was also increased by 25% comparedto the control group. The mean catalase enzyme activity in plants treated by resistance inducerswas 0.054 U/mL, while it was 0.111 U/mL in plants solely inoculated with bacteria. The highest SOD activity was recorded in potassium phosphite-treated plants inoculated with the pathogen. Mean catalase activity in inducer-treated plants was 0.052 U/ml, while it was 0.111 U/mlin these plants when inoculated with the pathogen. Malondialdehyde, as a reliable indicator of plant damage upon pathogen attack, exhibited the lowest content in succinic acid-treated plants 8 days after inoculation. This reduction was directly correlated with decreased bacterial spots on the leaves of plants treated with succinic acid. Our results show that potassium phosphite and succinic acid-induced effective defense responses in tomato plants against X. gardneri leading to reduced disease severity effect. According to the results, potassium phosphite andsuccinic acid may be used as potential resistance inducers in tomato plants against X. gardneri.