Induction of phenolics, lignin and key defense enzymes in eggplant (Solanum melongena L.) roots in response to elicitors

Abstract

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.

Key words: Catalase, chitosan, cinnamyl alcohol dehydrogenase, lignin, methyl jasmonate, methyl salicylate, phenylalanine ammonia lyase, peroxidase, salicylic acid, Solanum melongena.