title: Identification of Key Plant-Associated Volatiles Emitted by Heliothis virescens Larvae that Attract the Parasitoid, Microplitis croceipes: Implications for Parasitoid Perception of Odor Blends.
abstract: Herbivores emit plant-associated volatile organic compounds (VOCs) after feeding on plants. These plant-associated VOCs can be used by parasitoids to locate their hosts. It is hypothesized that certain compounds play key roles in the attractiveness of host-associated odor blends. The larval parasitoid, Microplitis croceipes (Hymenoptera: Braconidae) and its herbivore host, Heliothis virescens (Lepidoptera: Noctuidae), a major pest of cotton plant were used as model species to identify key compounds mediating attraction of parasitoids to hosts. Comparative GC/MS analyses of cotton-fed vs. artificial diet-fed hosts indicated that 12 of 17 compounds in the headspace of H. virescens larvae were exclusive to plant-fed hosts, and thus considered to be plant-associated. In order to identify key attractive compounds, a full blend of 15 commercially available synthetic compounds was modified by removing each of the 10 plant-associated compounds emitted by host larvae. In Y-tube olfactometer bioassays testing parasitoid responses to modified blends, 1-octen-3-ol, decanal, (E)-β-caryophyllene, α-humulene, α-farnesene, and β-pinene were identified as key compounds contributing to attractiveness of the natural blend of VOCs emitted by cotton-fed hosts. The results showed that while various host-associated compounds act in concert to serve as useful host location cues, only a fraction of the natural blend mediates attraction in parasitoids. Furthermore, the role of a compound is better assessed in the context of other compounds, and odor blends are better perceived as a whole rather than as individual components.
authors.affiliation: Department of Entomology & Plant Pathology, Auburn University, Auburn, AL, 36849, USA.
authors.forename: Tolulope
authors.initials: T
authors.lastname: Morawo
authors.affiliation: Department of Entomology & Plant Pathology, Auburn University, Auburn, AL, 36849, USA. fadamhy@auburn.edu.
authors.forename: Henry
authors.initials: H
authors.lastname: Fadamiro
mesh_terms: D000818:Animals; D003368:Gossypium / Q000737:chemistry*; D006927:Hymenoptera / Q000187:drug effects / Q000502:physiology*; D007814:Larva / Q000187:drug effects / Q000502:physiology*; D007915:Lepidoptera / Q000469:parasitology*; D009812:Odorants / Q000032:analysis*; D055696:Olfactory Perception / Q000187:drug effects*; D010058:Oviposition / Q000187:drug effects; D055549:Volatile Organic Compounds / Q000032:analysis / Q000494:pharmacology; D014835:Volatilization
chemical_list: D055549:Volatile Organic Compounds
keywords: Background odors; Contextual perception; Gas chromatography-mass spectrometry; Olfactometer