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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Chemistry Research » Research » Publications at this Location » Publication #98338
Title: VOLICITIN, AN ELICITOR OF MAIZE VOLATILES IN THE ORAL SECRETION OF SPODOPTERA EXIGUA: ITS ISOLATION AND BIO-ACTIVITY

Author
item TURLINGS, TED - UNIV. NEUCHATEL
item ALBORN, HANS - ENT. DEPT., UNIV. FLORIDA
item LOUGHRIN, JOHN - ENT. DEPT., UNIV. KY
item Tumlinson Iii, James

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: When beet armyworm caterpillars chew on corn or cotton leaves the plants emit an odor that attracts natural enemies of the caterpillar pests. These natural enemies, which parasitize the caterpillars, are effective biological control agents. Domestic varieties of corn and cotton, which have been bred for high grain and fiber production, have much reduced capabilities for production of the odors when compared to wild varieties. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, ARS, USDA, Gainesville, FL, have isolated a chemical from the oral secretions of the beet armyworm caterpillars that triggers the plant biochemical mechanisms to produce and emit the attractive odors. Corn seedlings incubated in very low concentrations of the pure natural chemical emit large quantities of odors that attract parasitic wasps that attack beet armyworm caterpillars. This research makes it possible to identify and synthesize volicitin, and then use it in pest management.

Technical Abstract: Plants respond to insect-inflicted injury by systemically releasing relatively large amounts of several volatile compounds, mostly terpenoids and indole. As a result, the plants become highly attractive to natural enemies of the herbivorous insects. In maize, this systemic response can also be induced by the uptake via the stem of an elicitor present in the oral secretions of caterpillars. Such an elicitor was isolated from the regurgitant of Spodoptera exigua larvae and identified as N-(17-hydroxylinolenoyl)-L-glutamine (Alborn et al., 1997, Science 276:945) and was named volicitin. Here we present details on the procedure that was used to isolate volicitin and the bio-assays that demonstrate its potency as an elicitor of maize volatiles; that attract parasitoids. With a series of purification steps using liquid chromatography, volicitin was separated from all other, inactive substances in the regurgitant of larvae of the noctuid moth S. exigua. Maize seedlings that were incubated in very low concentrations of pure natural volicitin, released relatively large amounts of terpenoids and became highly attractive to the parasitoid Microplitis croceipes. The identification of this and other such factors will allow us to determine the precise source and function of the caterpillar-derived elicitor, and better understand the evolutionary history of the phenomenon of herbivore-induced volatile emissions in plants.