Herbivory by Helicoverpa armigera unraveled defense‐driven metabolic reprogramming mediated by Terpene synthases ( CpTPS ) in Cajanus platycarpus

SUMMARY Cajanus platycarpus , a wild relative of cultivated pigeonpea, exhibits robust resistance to the pod borer, Helicoverpa armigera ; however, the contribution of terpenoid metabolism to this resistance has not been systematically examined. Here, we investigate the terpene synthase ( TPS ) gene family in C. platycarpus and its relation with continued herbivory. The C. platycarpus genome encodes 52 TPS genes distributed across 11 chromosomes, comprising both conserved TPS lineages and species‐specific expansions. Integrative analyses of phylogeny, synteny, and herbivory‐associated expression patterns prioritized CpTPS32 , CpTPS42 , and CpTPS47 as candidate TPS genes linked to herbivore‐responsive terpene emission patterns. These genes are connected with the production of a focused set of mono‐ and sesquiterpenes, including linalool, nerolidol, germacrene D, and α‐farnesene. Coherently, GC–MS/LC–MS profiling revealed recurrent herbivore‐induced shifts in the relative abundance of this restricted terpene blend. Heterologous expression of the selected CpTPS genes in Nicotiana benthamiana was linked with reduced insect damage and production of the target metabolites. Artificial diet assays with linalool and nerolidol suppressed larval growth and induced detoxification‐related cytochrome P450 gene expression in the larval midgut. Together, our findings identified a small subset of TPS genes and a concomitant terpene blend associated with herbivore‐responsive chemical defense in C. platycarpus , providing a framework for prioritizing the candidate genes for engineering enhanced pod borer resistance in pigeonpea.