REACTIVE OXYGEN SPECIES SIGNALING IN EGGPLANT IN RESPONSE TO RALSTONIA SOLANACEARUM INFECTION
S. Mandal, P. Acharya, I. Kar
This study is aimed at investigating reactive oxygen species formation, lipid peroxidation, induction of antioxidant enzymes and cell wall strengthening as initial responses of eggplant to Ralstonia solanacearum infection The oxidative burst triggered during the course of interaction may be an initial defense response of the host targeted against the invading bacterial pathogen. The concentration of H2O2 in inoculated roots was 53 μmol g-1 at 48 h post inoculation (hpi), which was about three times higher than in the control. The increase in O2.- generation resulting from inoculation with R. solanacearum was evident prominently from 24 hpi, but was highest at 48 hip. At 24 hpi, the increase in OH ̇ generation resulting from R. solanacearum inoculation was at 3.9 A/g/h. Lipid peroxidation was higher at later stage of eggplant-R. solanacearum interaction. The activities of the antioxidative enzymes, viz. superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) increased in response to pathogen inoculation. SOD activity was more than three times higher than in non- inoculated plants at 48 hpi. CAT activity showed a decrease after 30 hpi and finally it reached the level in control plants. The increase in activities of GPX and APX was significant in inoculated roots. The highest phenolic and lignin contents were determined at 54 hpi in the inoculated plants. However, the antioxidative system in the plant was rather weak and the rate of lipid peroxidation was higher. We conclude that the biochemical events favored R. solanacearum rather than the eggplant, making this host-pathogen interaction a compatible combination.