Jasmonic acid and herbivory differentially induce carnivore-attracting plant volatiles in lima bean plants

Lima bean plants respond to feeding damage of two-spotted spider mites (Tet ranychus urticae) with the emission of a complex blend of volatiles that ar e products of several different biosynthetic pathways. These volatiles attr act the carnivorous mite Phytoseiulus persimilis, a specialist predator of the spider mites that exterminates entire prey populations, and thus the vo latiles contribute indirectly to plant defense. The volatile blend constitu tes information to the carnivores, and blend composition is an important fa ctor in this. Jasmonic acid (JA) is involved in the signal transduction of this induced defense. Application of JA through the petiole of Lima bean pl ants induces a volatile blend that is similar, but not identical, to that e mitted by spider mite-infested plants. The induced volatiles originate from the lipoxygenase pathway, the shikimic acid pathway, and the isoprenoid pa thway. Among the induced bean plant volatiles are nitriles and oximes. Of a total of 61 components, 10 are emitted at significantly different rates. A mong these are the terpene (E)-4,8-dimethyl-1,3,7-nonatriene and the phenol ic methyl salicylate, two compounds that are known to attract P. persimilis . A crucial test for comparing the effect of spider mite damage and JA appl ication on volatile induction is the response of P. persimilis. The carnivo re is attracted by volatiles from JA-treated plants. Moreover, even treatme nt of Lima bean plants with methyl jasmonate vapor made the plants attracti ve to the carnivorous mites. However, the predators prefer the volatiles fr om spider-mite-infested Lima bean plants over those from JA-treated plants. Thus, chemical as well as behavioral analyses demonstrate that spider mite damage and JA treatment have similar, although not identical, effects on v olatile induction in Lima bean plants.