Role of defense enzymes and phenolics in resistance of wheat crop (Triticum aestivum L.) towards aphid complex

Herbivory damage leads to induction of rapid signals and responses in plants such as oxidative burst, accumulation of secondary metabolites and defensive proteins. Response of various defensive enzymes and secondary metabolites in flag leaf samples of six bread wheat varieties against aphid feeding was investigated. Six bread wheat varieties, namely PBW 621 and HD 2967 (timely sown irrigated), PBW 590 and PBW 658 (late sown irrigated), and PBW 644 and PBW 660 (timely sown rainfed) were grown under the aphid infested and uninfested conditions and were sampled at a regular interval to analyze the biochemical changes caused by aphid feeding. A tremendous increase in the overall activity of various enzymes namely superoxide dismutase, glutathione reductase, phenylalanine ammonia lyase and polyphenol oxidase was observed, all of which play an important role in plants defense towards aphid feeding. Each wheat genotype showed an overall difference in their defensive activity towards aphid feeding. However, certain genotypes under different conditions showed significantly less susceptibility towards aphid damage. Abbreviations: GR: glutathione reductase; HPR: host plant resistance; PAL: phenylalanine ammonia lyase; PPO: poly phenol oxidase; POD: peroxidase; SOD: superoxide dismutas