Elicitors are capable of mimicking the perception of a pathogen by a plant, thereby triggering induction of a sophisticated defense response in plants. In this study, we investigated an induced resistance in eggplant in respect to cell wall strengthening and defense enzyme activation affected by four elicitors such as, chitosan (CHT), salicylic acid (SA), methyl salicylate (MeSA) and methyl jasmonate (MeJA). The increase in total phenolic content of eggplant roots by the elicitors was significantly higher. Lignin deposition in the cell wall of eggplant roots was increased 5, 4, 3 and 3 times by SA, CHT, MeJA and MeSA at 96 h of elicitation, respectively. Phenylalanine ammonia-lyase (PAL) activity showed an increase of 4.7, 3.7, 3.5 and 3.2 times by SA, CHT, MeJA and MeSA at 36 h of elicitation, respectively. Highest activity of peroxidase (POD) was observed at 24 h after elicitation under the precise influence of CHT and SA. The activities of polyphenol oxidase (PPO), cinnamyl alcohol dehydrogenase (CAD) and catalase (CAT) were also increased several folds by the elicitors. Accumulation of phenolics and lignin in high amounts, together with higher level activity of major defense enzymes in response to the elicitors, may bolster eggplants in mounting practical and effective resistance against Ralstonia solanacearum, the devastating wilt pathogen.

The rhizobacterial isolates from different agro ecological region of West Bengal, used in this study, were identified as fluorescent pseudomonads based on biochemical and molecular characterization. Six effective antagonist isolates were selected for further studies of secondary metabolite (siderophore) production with respect to bacterial growth at different time intervals (6 to 96 h), the nature of siderophore production (hydroxamate and/or catecholate type), effect of iron supplementation at its different concentration on siderophore production and antagonistic potentiality. Observations of higher level of growth and siderophore production, for most of the isolates, were recorded after 72 h of incubation. The maximum zone of inhibition and siderophore production was recorded at 0.5 µM and the least at 10 µM iron concentration. With the gradual increase in iron supplementation in king's B medium, the siderophore production as well as in vitro antagonistic potentiality decreased in terms of enhancement of diameter of fungal mycelium and reduction of percent inhibition of pathogen by fluorescent pseudomonads in dual culture assay method.