Plants have evolved several adaptive strategies through physiological changes in response to herbivore attacks. Plant secondary metabolites (PSMs) are synthesized to provide defensive functions and regulate defense signaling pathways to safeguard plants against herbivores. Herbivore injury initiates complex reactions which ultimately lead to synthesis and accumulation of PSMs. The biosynthesis of these metabolites is regulated by the interplay of signaling molecules comprising phytohormones. Plant volatile metabolites are released upon herbivore attack and are capable of directly inducing or priming hormonal defense signaling pathways. Secondary metabolites enable plants to quickly detect herbivore attacks and respond in a timely way in a rapidly changing scenario of pest and environment. Several studies have suggested that the potential for adaptation and/or resistance by insect herbivores to secondary metabolites is limited. These metabolites cause direct toxicity to insect pests, stimulate antixenosis mechanisms in plants to insect herbivores, and, by recruiting herbivore natural enemies, indirectly protect the plants. Herbivores adapt to secondary metabolites by the up/down regulation of sensory genes, and sequestration or detoxification of toxic metabolites. PSMs modulate multi-trophic interactions involving host plants, herbivores, natural enemies and pollinators. Although the role of secondary metabolites in plant-pollinator interplay has been little explored, several reports suggest that both plants and pollinators are mutually benefited. Molecular insights into the regulatory proteins and genes involved in the biosynthesis of secondary metabolites will pave the way for the metabolic engineering of biosynthetic pathway intermediates for improving plant tolerance to herbivores. This review throws light on the role of PSMs in modulating multi-trophic interactions, contributing to the knowledge of plant-herbivore interactions to enable their management in an eco-friendly and sustainable manner.

Thirty genotypes of chilli were evaluated in RBD with three replications at vegetable research farm, CHF, CAU, Pasighat, Arunachal Pradesh, India during kharif, 2011. Variability, correlation and path analysis were carried out to study the character association and contribution, respectively. Analysis of variance revealed significant differences among the genotypes for all traits. High PCV and GCV, heritability, genetic advance were observed for days to first flowering, plant height, number of seed per fruit, number of fruit per plant, ascorbic acid and fruit yield per plant. Correlation indicated that fruit yield per plant was positively and significantly correlated with number of branch per plant, number of fruit per plant and chlorophyll content while negative and significant association was established with ascorbic acid content. Maximum positive direct effect on fruit yield per plant was imposed by fruit weight, number of fruit per plant, number of seed per fruit and capsaicin content.

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