Identification Of Preference Volatiles To Harmonia Axyridis In The Aphid-infested Plants And Exploration Of Olfactory Related Genes

Harmonia axyridis(Coleoptera:Coccinellidae)is a common natural enemy insect in North China farmland ecosystem,mainly preying on aphids.Previous studies have found that adults prefer the aphid-infested plant in the field.Based on the principles and methods of chemical ecology,we studied the mechanism of chemical communication in the perference of Harmonia axyridis to aphid-infested plants,meanwhile we explored and analyzed the olfactory-related genes of Harmonia ayridis The main results are as follows:The influence of prey(aphids)and 8 kinds of host plant volatile compounds on the olfactory responses of H.axyridis adults were examined in two-choice tests using a Y-tube olfactometer.We found that aphid-infested plants were most attractive to H.axyridis males and females compared with aphid,healthy plant and blank control.Moreover,using coupled gas chromatography-electroantennogram detection(GC-EAD)and gas chromatography-mass spectrometer(GC-MS),we identified totally 7 components in 8 plant species that elicited significant electrophysiological activity from both H.axyridis male and female antennae.In behavioral choice assays,ladybirds significantly preferred 5 kinds of chemicals(p-Diethylbenzene,3-Ethylacetopheneone,1,2-Diethylben,a-Pinene and Butyl Acrylate)from plants infested with aphids,whereas showed no obvious response to the other two(4-Ethyl benzaldehyde,4-Ethylacetopheneone).Next,in a open-field test using barrel traps,H.axyridis were significantly attracted to these 5 kinds of chemicals(p-Diethylbenzene,3-Ethylacetopheneone,1,2-Diethylben,?-Pinene and Butyl Acrylate)with the higher concentration of 100 mg/ml dilution.By using High-throughput sequencing and bioinformatics analysis method,we have discovered 57 olfactory related genes,including 30 odorant binding protein and 27 chemosensory protein.The expression profiles of OBP1,OBP2,OBP3,CSP2,CSP5,CSP10 in different tissues were measured by real-time qPCR and RT PCR.The results showed that the OBP2,OBP3,CSP2,CSP5,and CSP10 genes had the highest expression levels in antennae,and OBP1 also had higher expression levels in the antennae,which was only lower than the expression levels in the gonads,demonstrating that antennae play an important role in the process of perceiving and identifing the external odor of Harmonia axyridis.The present study preliminarily identified the olfactory recognition mechanism of Harmonia axyridis and provided the main basis for promoting its important biological control in farmland.