Study On The Perception Mechanisms Of Unsaturated Cuticular Hydrocarbons In Males Of The Yellow Peach Moth(Conogethes Punctiferalis)

Yellow peach moth, Conogethes punctiferalis, belongs to Lepidoptera:Crambidae. It is widely distributed in East Asia, South Asia, Australia and many regions in China. Larvae of this species are typically polyphagous pests of many crops. Currently, control methods of this species mainly include agricultural, biological and chemical controls. Chemical method is still the primary one yet. However, it has some typical disadvantages, such as residue, resistance, harm of the natural enemies. Recently, owing to the characteristics of being green, pheromones have been put into pest forecast and control. Researchers firstly identified the sex pheromone components of yellow peach moth to be a binary mixture of (E)-10-hexadecanal and (Z)-10-hexadecanal (an aldehydes pheromone). But this binary mixture has experienced low performance in field test. Later, researchers found that two hydrocarbon pheromones of (Z3, Z6, Z9)-tricosatriene and (Z9)-heptacosene, identified in female body wax extracts, significantly enhanced attractiveness of the aldehydes pheromone in wind tunnel tests, but the perception mechanisms of the male moth is unknown, which would hamper practical applications. To make this issue clear, we have conducted EAG, GC-EAD, the wind tunnel test and transcriptome sequencing of the antennae of the male moths. Here we listed the main results of this study:1. In EAG trials, when different concentrations of aldehydes were used to test the left antenna or the right one, results indicated that the left or right antennae showed no difference in EAG responses, which provided evidence that we could choose antennae randomly in the following experiments. Next, in the trials of testing male moths to (Z3, Z6, Z9)-tricosatriene and (Z9)-heptacosene, no differences in antenna responses were found among 4 concentrations,0.01,0.1,1.0 and 10 female equivalents. Moreover, these responses to hydrocarbons were much lower than that of aldehydes. And no differences were found between any of hydrocarbons responses and that of the hexane control, respectively. Finally, when these two hydrocarbons were mixed with aldehydes, EAG relative values showed no obvious changes.2. In the following GC-EAD trials, when (Z3, Z6, Z9)-tricosatriene or (Z9)-heptacosene was tested respectively, no EAG signals were detected in male antennae. When the mixture of aldehydes and hydrocarbons were tested, EAG signals were found only in corresponding position of aldehydes.3. In wind tunnel tests, a metal net was set close to a pheromone source (a filter paper loaded with chemicals) to keep males from directly contacting the filter paper. Results showed that a male response to the mixture of aldehydes and hydrocarbons was as high as that of crude pheromone extracts, both of which were statistically higher than aldehydes. In another wind tunnel test, the metal net was removed but meanwhile hydrocarbons and aldehydes were loaded respectively on two different filter papers, which were hung separately at different locations in the wind tunnel (horizontal radial locations 2 cm away and axially hung 10 cm away). In all sets, male moths responded only to aldehydes but not to hydrocarbons. And the response was the same as that when aldehydes was tested alone.4. Finally, atranscriptome sequencing was conducted to search for candidate genes coding odorant binding proteinssuch as general odorant binding protein (GOBP) pheromone binding protein (PBP). Then, a phylogenetic tree was made to make comparisonsamong the Conogethes punctiferalis, Bombyx mori and Helicoverpa armiger. As a result,28 OBP genes were identified in the male antennae, including 5 GOBP genes and 5PBP genes.Taken all results together it could be concluded that in yellow peach moth, males are able to perceive hydrocarbon pheromones in an olfactory way inspite of a taste sensing. Compared to olfactory responses to aldehydes in males, hydrocarbons olfaction was too weak to be detected by EAG and GC-EAD, so we may infer it is lower than the detection limit of EAG. Additionally, results of wind tunnel tests showed that male moths were able to percept hydrocarbon pheromones, only on the condition that hydrocarbons and aldehydes were released from a pinpoint at the same time. However, this will be further testified through more detailed electrophysiological tests and moreover, a relationship between males olfactory and behavioral responses to unsaturated hydrocarbons is yet to be studied.