Location: Pest Management ResearchTitle: Synthetic cis-jasmone exposure induces wheat and barley volatiles that repel the pest cereal leaf beetle, Oulema melanopus L) Author
Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/26/2013
Publication Date: 5/1/2013
Publication URL: http://handle.nal.usda.gov/10113/56455
Citation: Delaney, K.J., Wawrzyniak, M., Lemanczyk, G., Wrzesinkska, D., Piesik, D. 2013. Synthetic cis-jasmone exposure induces wheat and barley volatiles that repel the pest cereal leaf beetle, Oulema melanopus L. Journal of Chemical Ecology. 39(5): 620-629. Interpretive Summary: The plant volatile organic compound, (Z)-jasmone (also called cis-jasmone), is being increasingly recognized as an important plant semiochemical that can influence plant resistance to herbivores, and attract or repel herbivores and their natural enemies. However, whether plant volatile induction is influenced by cis-jasmone exposure dose and duration, and whether plant exposure influences cereal leaf beetle (CLB; a widespread invasive US small grain pest) attraction or repellence, has not been studied so we conducted studies with spring barley and winter wheat. There were eight volatiles induced after cis-jasmone exposure to wheat or barley: four terpenes commonly induced after insect herbivory, indole, and three green leaf volatiles usually induced after injury. Despite a 10,000-fold difference between the highest and lowest cis-jasmone exposure doses, there was only 50-250% higher emission levels of volatiles from the two cereals exposed to the highest cis-jasmone dose. There was also often a 50-100% greater emission level of most volatiles when cis-jasmone exposure lasted 6 hours compared to 1 hour. CLB adults were repelled more by barley than wheat volatiles after plant cis-jasmone exposure, with stronger repellence: by females than males, at higher cis-jasmone exposure dose and duration, and when air with plant volatiles was delivered to beetles at a faster rate. Females were attracted to plants not exposed to cis-jasmone but only when plant volatiles were delivered to beetles at the highest airflow rate. These lab results suggest that barley and wheat volatile induction after cis-jasmone exposure might repel CLB, but this would need to be confirmed with field studies. Also, CLB repellence responses were generally stronger to barley than wheat, which may relate to higher barley volatile emission levels than wheat at each cis-jasmone exposure dose * duration. CLB was repelled by the two highest test doses of both terpene and green leaf volatile synthetic blends, but were attracted to the lowest dose of the green leaf volatile blend. These results suggest that terpenes and indole may be somewhat more important volatiles for barley and wheat repellence to CLB, while supporting a previous study suggesting that GLV may play a role in CLB attraction.
Technical Abstract: The plant semiochemical cis-jasmone primes/induces plant resistance to deter herbivores and attract natural enemies. We studied the induction of volatile organic compounds (VOCs) in winter wheat and spring barley after exposure of plants to three synthetic cis-jasmone doses (50 ml containing 1, 100, and 10000 ng cis-jasmone per ml) and durations of exposure (1, 3, and 6 hr). Cereal leaf beetle, Oulema melanopus, adult behavioral responses were examined in a Y-tube olfactometer to cis-jasmone induced plant VOC bouquets and to two synthetic blends of VOCs (3 green leaf volatiles (GLVs); 4 terpenes + indole). In both cereals, eight VOCs ((Z)-3-hexanal, (Z)-3-hexanol, (Z)-3-hexanyl acetate, (Z)-ß-ocimene, linalool, ß-caryophyllene, (E)-ß–farnesene and indole) were usually induced 100- to 1000-fold after cis-jasmone exposure. The degree of VOC induction in both cereals was usually positively and linearly associated with increasing exposure dose and duration. However, the VOC emission rate was only ~ 2-fold greater from plants exposed to the highest vs. lowest cis-jasmone exposure doses (10000-fold difference) or durations (6-fold difference). Male and female O. melanopus were deterred by both cereal VOC bouquets after plant exposure to the high cis-jasmone dose (10000 ng per ml), while females were also deterred after plant exposure to the low dose (1 ng per ml) but attracted to unexposed plant VOC bouquets. Both O. melanopus sexes were repelled by terpene/indole and GLV blends at two concentrations (25 ng per min; 125 ng per min), but attracted to the lowest dose (1 ng per min) of a GLV blend. It is possible that the biologically relevant low cis-jasmone dose has ecological activity and potential for inducing field crop VOCs to deter O. melanopus.