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Volatile induction of infected and neighbouring uninfected plants potentially influence attraction/repellence of a cereal herbivore

Piesik, D., Panka, D., Jeske, M., Wenda-Piesik, A., Delaney, K. J., Weaver, D. K.
Journal of applied entomology 2013 v.137 no.4 pp. 296
Fusarium, Osmia, acetates, barley, corn, grain crops, herbivores, insect attractants, insect repellents, leaves, linalool, oxides, plant pathogens, volatile organic compounds, wheat
Plant infection by pathogens can induce volatile organic compounds (VOCs). We infected ‘McNeal’ wheat and ‘Harrington’ barley with a Fusarium spp. blend (graminearum, avenaceum, and culmorum). Both cereals had highest VOC induction 14 d after pathogen introduction, significantly slightly lower induction occurred at 7 d, but no induction at 1d. The induced VOC bouquet for both cereals included green leaf volatiles (GLVs; (Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexenol, (E)-2-hexenol, (Z)-3-hexenyl acetate, 1-hexenyl acetate), terpenes ((Z)-ocimene, '-linalool, linalool oxide, '-caryophyllene), and benzyl acetate. Uninfected individuals of both cereals had significant VOC induction from a neighboring infected conspecific plant where degree of induction was negatively related to infected plant distance. Y-tube tests showed that female and male O. cyanella Voet. were significantly attracted to (Z)-3-hexenal and (Z)-3-hexenyl acetate at 300 and 1500 ng h-1, and repelled from both GLVs, (Z)-'-ocimene, and linalool at 7500 ng h-1. Thus, pathogen infection of both cereals induced VOCs as induced concentrations increased over time and induced neighboring uninfected plant VOCs. This may influence herbivores, as O. cyanella had dose-dependent attraction and/or avoidance of some VOCs, different than previously tested O. melanopus that only had attraction responses to three VOCs common to maize, barley, and wheat cereals.