Plant Secondary Metabolites as a Tool to Investigate Biotic Stress Tolerance in Plants: A Review

Plants have a large diversity of metabolites in order to carry out the complicated plant metabolic pathway in a coordinated manner under normal as well as stressful conditions. These metabolites are further subdivided into primary metabolites which are responsible the for main metabolic pathways that are critical for the survival of plants and secondary metabolites which are not necessary for the main metabolic pathway for growth and development but are involved in developing the ability of the plants to interact with the surrounding adverse environment. Plants produce a diversity of secondary metabolites (PSMs) that serve as defense compounds against herbivores and microorganisms. In addition, some PSMs attract animals for pollination and seed dispersal. Pathogens gain entry into host cell, reproduce there and use biological machinery of host plants which is threat to global crop production. Integrated management strategies based upon minimizing population and use of resistant cultivars can address this potential problem. In the developing world, farmers are less likely to adopt these approaches instead they prefer the use of chemical pesticides. Reckless use of chemical pesticides is destroying our ecosystem, which is why ecofriendly alternatives, like plant-based metabolites to control pathogens, must be explored. Studies conducted on different plant metabolites reported that these metabolites can potentially combat plant pathogens. In this study, we also discuss some of the plant secondary metabolites including alkaloids, flavonoids and phenolics, and antioxidant enzymes like peroxidase, polyphenol oxidase, and chitinase.