Untitled

Abstract

Egg deposition of the elm leaf beetle Xanthogaleruca luteola causes the emission of volatiles from its food plant, Ulmus minor. These volatiles are exploited by the egg parasitoid, Oomyzus gallerucae, to locate its host. In contrast to other tritrophic systems, the release of volatiles is not induced by feeding but by egg deposition. Previous investigations showed that the release is systemic and can be triggered by jasmonic acid. Comparison of headspace analysis revealed similarities in the blend of volatiles emitted following egg deposition and feeding. The mixture consists of more than 40 compounds; most of the substances are terpenoids. Leaves next to those carrying eggs emit fewer compounds. When treated with jasmonic acid, leaves emit a blend that consists almost exclusively of terpenoids. Dichloromethane extracts of leaves treated with jasmonic acid were also investigated. After separation of extracts of jasmonate induced elm leaves on silica, we obtained a fraction of terpenoid hydrocarbons that was attractive to the parasitoids. This indicates that jasmonic acid stimulates the production of terpenoid hydrocarbons that convey information of egg deposition to the parasitoid.

Chemical composition of the essential oils of Lantana camara L. occurring in south China

“…β-caryophyllene had a highly significant effect on mortality, 27 correlates with reduction in the level of lepidopteran herbivory in several populations of the tropical leguminous tree Hymenaea stigonocarpa 28 and attracts adult predatory green lacewings, Chrysopa carnea, 29 while Bernhad Weissbecker et al 30 demonstrated that the two-spotted predaceous stinkbug, Perillus bioculatus, was attracted towards the sesquiterpenes β-caryophyllene, germacrene D, bicyclogermacrene and α-humulene in volatiles released from damaged potato plant by Colorado potato beetle. By separating apolar terpenoid hydrocarbons from more polar compounds using column chromatography on silica, Wegener et al 31 showed that a volatile blend containing α-elemene, δ-cadinene, α-humulene, germacrene D and (E,E)-α-farnesene, emitted in jasmonate-induced elm leaves, was exploited by the specialist parasitoid Oomyzus gallerucae in locating its host, the elm leaf beetle Xanthogaleruca luteola. In addition, while 1,8-cineole and δ-3-carene have been shown to be involved in cases of both direct plant defence 32,33 and pollination, 34 the former have also been reported in allelopathic effects as toxic, deterrent or inhibitory compounds, 35 repellency and toxicity against three stored product coleopterans: Callosobruchus maculates F., Rhyzopertha dominica F. and Sitophilus oryzae L. 36 Besides the isolates, the whole essential oils also exhibit ovicidal, insecticidal, antifeedant, attractant, repellent, antiviral and anti-juvenile hormone activities.…”

A Non-targeted Metabolomics Approach Unravels the VOCs Associated with the Tomato Immune Response against Pseudomonas syringae

“…Terpenoids induced by herbivores act in plant defense by attracting insect predators, and by acting as repellents or toxic compounds (Turlings and Tumlinson, 1992; Wegener et al, 2001). Besides, they have been associated to resistance against downy mildew in grapevine (Alarcón et al, 2015).…”

Perception, signaling and molecular basis of oviposition-mediated plant responses

“…Indirect defenses include the emission of a bouquet of volatile compounds that attract egg parasitoids. Studies in elm and pine demonstrated that specific egg-induced terpenoids are attractive to parasitoids, both in the laboratory and in the field (Hilker et al 2002a; Mumm et al 2003; Mumm and Hilker 2005; Büchel et al 2011; Wegener et al 2001). Eggs also induce indirect defenses by triggering changes in leaf surface chemistry as in Brassicaceae.…”