Synthetic Cis-Jasmone Exposure Induces Wheat and Barley Volatiles that Repel the Pest Cereal Leaf Beetle, Oulema melanopus L.

Abstract

The plant semiochemical cis-jasmone primes/induces plant resistance that deters herbivores and attracts 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 μl of 1, 100, and 1 × 10(4) ng μl(-1)) and durations of exposure (1, 3, and 6 h). 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)-β-ocimene, linalool, β-caryophyllene, (E)-ß-farnesene, and indole] were induced 100- to 1000-fold after cis-jasmone exposure. The degree of induction in both cereals was usually positively and linearly associated with increasing exposure dose and duration. However, VOC emission rate was only ~2-fold greater from plants exposed to the highest vs. lowest cis-jasmone exposure doses (1 × 10(4) 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 (1 × 10(4) ng μl(-1)), while females were also deterred after plant exposure to the low dose (1 ng μl(-1)) but attracted to unexposed plant VOC bouquets. Both O. melanopus sexes were repelled by terpene/indole and GLV blends at two concentrations (25 ng · min(-1); 125 ng · min(-1)), but attracted to the lowest dose (1 ng · min(-1)) 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.

Methyl Jasmonate Affects Population Densities of Phytophagous and Entomophagous Insects in Wheat

“…However, in our previous study, we found that the outcome of CJ on wheat stem sawflies is influenced by the sampling method, with more consistent results obtained from yellow sticky traps and indicating that CJ is repellent to wheat stem sawfly adults (Bayram and Tonğa, 2017). CJ-treated wheat plants release a group of HIPVs, one of which ((Z)-3-hexenyl acetate) repels the wheat stem sawfly C. cinctus at high doses while attracting it at lower concentrations (Piesik et al, 2008;Delaney et al, 2013). The same very high MEJA doses that we used in our study induced faster maturation of wheat plants in another study (Beltrano et al, 1998); therefore, in our field experiments, such faster growth may have limited the production of HIPVs like (Z)-3-hexenyl acetate, causing the compounds to remain at attractive (lower) concentrations after MEJA treatment.…”

“…Studies on the behavioral responses of Episyrphus balteatus, another hoverfly species, revealed that this hoverfly employs a composition of cues consisting of plant volatiles (i.e., green leaf volatiles and terpenoids) and a host pheromone(s) (Verheggen et al, 2008). Exogenous CJ application caused wheat plants to release volatiles such as (Z)-3-hexen-1-ol, which was found to contribute to host-plant locating and ovipositional behavior of the hoverflies (Verheggen et al, 2008;Delaney et al, 2013). A possible explanation is that the phytotoxic effects of MEJA may change both the chemical profile and the visual appearance of plants so that hoverflies may fail to locate their prey.…”

Response of mated insects of both sexes of granary weevil to blends of volatiles - short communication

“…Synthetic volatiles were obtained from Sigma-Aldrich (Chemical Co. Inc., Poznań, Poland), purity between 85 and 99%. Cereal compounds were selected based on their presence in cereal grains (Germinara et al 2010;Piesik et al 2011Piesik et al , 2014Delaney et al 2013;Piesik & WendaPiesik 2015). To screen behavioural activity of the pest volatile compounds were tested in six blends at four concentrations (1, 10, 100, 1000 ng/min) compared to the absence of the compound (0).…”

Sitophilus granarius responses to blends of five groups of cereal kernels and one group of plant volatiles

“…Yet, a caveat of caution needs to be pointed out concerning ecological and evolutionary aspects of VOC induction (Kessler and Heil, 2011). An insect dose response to an individual plant VOC can reveal the range of concentrations over which herbivore or parasitoid attraction or repellence occurs (Delaney et al, 2013;Piesik et al, 2011aPiesik et al, , 2014.…”