Uncovering the Critical Role of Herbivore-Induced DMNT in Enhancing Cowpea's Multifaceted Defense to Liriomyza sativae.

Understanding the roles of herbivore-induced plant volatiles (HIPVs) in regulating plant-herbivore-natural enemy interactions is essential for developing integrated pest management strategies. In this study, we found cowpea infested by leafminers (Liriomyza sativae) repelled the herbivores and attracted their natural enemy Neochrysocharis formosa, accompanied by the emission of large amounts of (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). Bioassays confirmed that DMNT simultaneously repelled L. sativae and attracted N. formosa. In addition, DMNT triggered jasmonic acid (JA) and salicylic acid (SA) biosynthesis in neighboring plants, activating plant-to-plant defense signaling. Further assays demonstrated that the enhanced expression of the nerolidol synthase gene VuNES, mediated by JA signaling, was the key factor promoting DMNT emission. These findings suggest that DMNT plays an important role in mediating tritrophic interactions among cowpea, leafminers, and parasitoid wasps, and elucidate the mechanism underlying its herbivory-induced emission. Our study provides a theoretical foundation for developing sustainable, DMNT-based strategies for integrated pest management.