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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 #123435
Title: IN VIVO VOLATILE EMISSIONS FROM PEANUT PLANTS INDUCED BY SIMULTANEOUS FUNGAL INFECTION AND INSECT DAMAGE

Author
item CARDOZA, YASMIN - ENT. DEPT, UNIV FLORIDA
item ALBORN, HANS - ENT DEPT, UNIV FLORIDA
item Tumlinson Iii, James

Submitted to: Journal of Chemical Ecology
Publication Type: Proceedings
Publication Acceptance Date: 9/10/2001
Publication Date: 2/20/2002
Citation: N/A

Interpretive Summary: Plants are constantly under attack by both insect herbivores and pathogens like molds. To overcome the attack of insect pests plants release air borne chemicals that attract insects that are enemies of the herbivores. However, the effects of attack by both insect herbivores and pathogens on plant defenses are poorly understood. Scientists at the Center for Medical Agricultural and Veterinary Entomology, USDA-ARS, Gainesville Florida, have been studying the effects of attack on plants by both the beet armyworms an herbivorous insect and white mold fungus. The results of their studies have shown that beet armyworms fed significantly more on white mold infected peanuts than on healthy plants. The chemicals released by white-mold infected peanuts were significantly different from those emitted by undamaged plants. However, peanut plants infected with the white mold and then exposed to beet armyworm damage released all the volatiles emitted by healthy plants fed on by beet armyworms, and those emitted by plants in response to white mold infection alone. This indicates that, although mold infested plants are more apparent to insect herbivores, after insect attack the plant is capable of producing all of the chemicals required to attract predators of the insect herbivores. Thus, infestation by mold does not compromise the plants defenses to insect attack.

Technical Abstract: Peanut plants, Arachis hypogaea, infected with white mold, Sclerotium rolfsii, emit a blend of organic compounds that differs both quantitatively and qualitatively from the blend emitted from plants damaged by beet armyworm (BAW), Spodoptera exigua, larvae or from uninfected, undamaged plants. Attack by BAW induced release of lipoxygenase products (hexenols, hexenals and hexenyl esters), terpenoids and indole. The plant-derived compound methyl salicylate and the fungal-derived compound 3-octanone were found only in head space samples from white mold infected plants. White mold-infected plants exposed to BAW damage released all the volatiles emitted by healthy plants fed on by BAW in addition to those emitted in response to white mold infection alone. When BAW larvae were given a choice of feeding on leaves from healthy or white mold infected plants, they consumed larger quantities of the leaves from infected plants. Exposure to commercially available (Z)-3 hexenyl acetate, linalool and methyl salicylate, compounds emitted by white mold infected plants, significantly reduced the growth of the white mold in solid-media cultures. Thus emission of these compounds by infected plants may constitute a direct defense against this pathogen.