Methyl hexenoate and linalool emitted by hot peppers repel western flower thrips (Frankliniella occidentalis) and attract their predator (Orius laevigatus)

A plant emits diverse volatile compounds and communicates with other organisms at different trophic levels. Hot pepper, Capsicum annuum, leaves produced different compositions of 41 organic compounds upon an infestation by the western flower thrips, Frankliniella occidentalis. These compounds induced a non-preference behavior to the thrips while they attracted a natural enemy, Orius laevigatus. Among the differentially emitted compounds, Z-3-methyl hexenoate (MeH) and linalool repelled the herbivore but attracted the predator. MeH or linalool biosynthesis was suppressed by virus-induced gene silencing of hydroperoxide lyase (HPL) or linalool synthase (LS) expression in the hot pepper and led to significant malfunction in the tri-trophic communication. This communication was mediated by jasmonic acid (JA), but not salicylic acid, signal in the hot pepper. Plant growth-promoting rhizobacteria also induced the antixenosis of hot peppers through JA signaling. Hot peppers resistant against the thrips were positively correlated with HPL or LS expression levels.