Antagonism between herbivore-induced plant volatiles and trichomes affects tritrophic interactions

We used tomato genotypes deficient in the jasmonic acid (JA) pathway to study the interaction between the production of herbivore-induced plant volatiles (HIPVs) that serve as information cues for herbivores as well as natural enemies of herbivores, and the production of foliar trichomes as defence barriers. We found that jasmonic acid-insensitive1 (jai1) mutant plants with both reduced HIPVs and trichome production received higher oviposition of adult leafminers, which were more likely to be parasitized by the leafminer parasitoids than JA biosynthesis spr2 mutant plants deficient in HIPVs but not trichomes. We also showed that the preference and acceptance of leafminers and parasitoids to trichome-removed plants from either spr2 or wild-type (WT) genotypes over trichome-intact genotypes can be ascribed to the reduced trichomes on treated plants, but not to altered direct and indirect defence traits such as JA, proteinase inhibitor (PI)-II and HIPVs levels. Although the HIPVs of WT plants were more attractive to adult insects, the insects preferred trichome-free jai1 plants for oviposition and also had greater reproductive success on these plants. Our results provide strong evidence that antagonism between HIPV emission and trichome production affects tritrophic interactions. The interactions among defence traits are discussed.