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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 #77020


item Pare, Paul
item Tumlinson Iii, James

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: When cotton plants are damaged by beet armyworm caterpillars feeding on the leaves they emit an odor, comprised of a blend of volatile chemicals, that attracts natural enemies of the caterpillars. Scientists at the Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL, have discovered that several of the constituents of this odor are freshly synthesized by the plants in direct response to the caterpillar feeding. Furthermore, this synthesis can be triggered by application of oral secretions of the caterpillars to mechanical wounds on the leaf surfaces, but not by mechanical wounding alone. Plants that are not wounded do not release these odors. When the component of the oral secretion of the caterpillars is identified and produced synthetically it may be useful in inducing plants to recruit natural enemies of insect pests. These results also indicate that the synthetically produced substance from caterpillar oral secretions may be useful in inducing plants to produce chemicals that can be used for industrial and medicinal purposes.

Technical Abstract: Cotton plants (Gossypium hirsutum L.) release elevated levels of volatiles in response to insect feeding on the leaves which can serve as a chemical signal in attracting natural enemies of the herbivore to the damaged plant. Pulse-labeling experiments with carbon-13 dioxide demonstrated that many of the acyclic terpenes including (E,E)-alpha- farnesene, (E)-beta-farnesene, (E)-beta-ocimene, linalool, (E)-4,8- dimethyl-1,3,7-nonatriene, and (E,E)-4,8,12-trimethyl-1,3,7,11- tridecatetraene, as well as indole were released in response to de novo biosynthesis. In contrast, several cyclic terpenes, butyrates, and green leaf volatiles of the lipoxygenase pathway were released from storage or synthesized from stored intermediates. Analysis of volatiles from artificially damaged plants, with and without beet armyworm (Spodoptera exigua Hubner) oral secretions exogenously applied to the leaves, as well as volatiles from beet armyworm damaged and undamaged control plants demonstrated that the application of the caterpillar oral secretion increased both production and release of several of the volatiles that were synthesized de novo in response to insect feeding. These results establish that the plant plays an active and dynamic role in mediating the interaction between herbivores and natural enemies of herbivores.