Location: Pest Management ResearchTitle: Volatile induction of infected and neighbouring uninfected plants potentially influence attraction/repellence of a cereal herbivore) Author
Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2012
Publication Date: 5/1/2013
Publication URL: http://handle.nal.usda.gov/10113/56749
Citation: Piesik, D., Panka, D., Jeske, M., Wenda-Peisik, A., Delaney, K.J., Weaver, D.K. 2013. Volatile induction of infected and neighbouring uninfected plants potentially influence attraction/repellence of a cereal herbivore. Journal of Applied Entomology. 137(4): 296-309. Interpretive Summary: Plants can be attacked by different pathogens and herbivores, which can reduce yields of agricultural crop species. One way plants respond to biotic attack is to induce and emit volatile organic compounds into the air, which may deter the attacker, attract to the plant natural enemies of the attacker, or alter attractiveness of the injury plant to other attackers. Here, we examined volatile organic compound induction after attack by one biotic Fusarium pathogens on wheat and barley plants at 1, 7 and 14 days post-infection, whether neighboring uninfected plants also induced volatiles when 1m or 3m from an infected plant, and a congener (different species within same genus) of the cereal leaf beetle (beetle pest species of small grains in Europe and the USA) was attracted or repelled to the most abundantly induced volatiles (each tested separately with the insect). There was no significant volatile induction at 1d post-infection, and neighboring plants had no volatile induction when near a 1d infected plant. However, at 7 days post-infection there were ten volatiles induced by both infected wheat and barley plants. Neighboring uninfected wheat and barley plants had significant induction of all ten volatiles when near an infected plant of the same species, and the degree of induction was negatively related to distance from the infected plant (infected plant > uninfected plant at 1m > uninfected plant at 3m > control uninfected, unexposed plant). The volatile induction trends were the same at 14 days post-infection, though there were slightly greater emission levels at 14 days vs. 7 days post-infection. At relatively lower doses closest to actual infected plant volatile emission levels, a congener of the cereal leaf beetle was attracted to 2 of the volatiles, but repelled at higher doses to these two volatiles and two additional volatiles. These results contrast with behavior of the cereal leaf beetle tested with three of the same compounds induced by pathogen infection of maize, where the cereal leaf beetle only exhibited attraction responses to tested volatiles. Thus, even congeneric beetle pest and non-pest species can have different behavioral responses to plant volatiles, and so could be differentially attracted or repelled when their host plant is attacked by a different organism. These results are of interest to those interested in understanding how plant attack by one organism (pathogen) can influence volatile responses of neighboring uninjured plants and responses by different groups of other potential attackers (e.g., herbivore) to suggest whether the plant would become more or less attractive as a feeding host.
Technical Abstract: 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.