Study On Semiochemicals Of Xylotrechus Rusticus L.

Xylotrechus rusticus is a kind of newly important bark pests which break out to be the disaster in the Northeast in China in recent years.It has brought great difficulties to the control of this pest because they bore into the trunk of trees.Poplar is the main afforestation species in the Northeast area,nowadays some areas are suffering from X.rusticus,and they bring a serious threat to the development of local forestry.For searching the way of ecological control on X.rusticus,this paper focused on the semiochemicals involved in the communication between the longicorn beetles,the beetles and plants,to explore the function of these semiochemicals and strive to find a single compounds or mixtures of different compounds which have biological activity for X.rusticus,and to provide a theoretical basis for the ecological control of the pest.In this experiment,ten kinds of poplar bark volatiles were extracted from 4 sensitive poplar species which are Populus.ussuriensis,P.pseudo-simonii,P.simonii and P.pseudo-simonii×P.nigra,and 6 kinds of resistance species which are P.berolinensis,P.simonii×P. nigra,P.russkii,P.alba×P.berolinensis,Populus x xiaozhuanica W.Y.Hsu et Liang cv. 'Baicheng-2' and P.stalintz,using steam distillation and supersonic extraction,respectively; Summa canister was adopt to collect trunk volatiles from 5 kinds of poplar,including P. simonii,P.berolinensis,P.alba L.×P.berolinensis,P.pseudo-simonii and P.simonii×P. nigra,applying the combination of pre-enrichment systems and gas chromatography-mass spectrometry(GC-MS) to analyse chemical composition of those volatiles.The analysis results showed that,in the non-oviposition period of longicorn beetles,all of those ten kinds of poplar barks extractions contains hexanal,salicylaldehyde,tetradecanal,hexadecanal,2,6-ditertbutyl-4-methyl phenol,linoleic acid,hexadecanoic acid and 11,14,17-eicosatrienoic acid,methyl ester,and these compounds were contained in the extracts obtained from different methods. The compounds contained in the volatiles obtained from ultrasonic extraction were more than that contained in those volatiles obtained by steam distillation extraction.Special compounds were found in those volatiles extracted from the insect resistance species such as P.alba L.×P. berolinensis and P.berolinensis.Those specials compounds are zingiberene,γ-muurolene, alloaromadendrene,a-muurolene,d-cadinene and camphor.During the oviposition period, using summa canister sampling,1-[4-hydroxy benzyl]-6-methoxy-3,4-Dihydroisoquinolin-7-ol were common component from P.simonii×P.nigra,P.berolinensis and P.alba×P. berolinensis with high insect-resistant,and the content were more than 20%,in which the content of P.simonii×P.nigra was the highest,reaching 83.90%.In volatiles from species with low insect-resistant,the content of(1R)-a-pinene from P.simonii was the highest,β- pinene and bornyl acetate were important components in P.pseudo-simonii.In the steam distillation extractions,the content of(1R)-a-pinene,eucalyptol and ethyl acetate was higher in volatiles from poplar species with low level of insect-resistant,β-pinene,2,4-Decadienal,1,2-cyclohexanedione,ethyloxy-ethylene and pyrazole usually have higher concentration in those volatiles from poplar species with higher insect-resistance.The differences of chemical composition and content in volatiles from poplar trunks with different insect-resistance level might be the main factors lead to the difference of insect behaviors and as well as the reason for insect-resistance of trees.The steam distillation extractions from bark of ten poplar species were used to test electrophysiological and behavioral response of both sexes of X.rusticus adults,the results primarily ascertained that volatiles from P.simonii×P.nigra and P.pseudo-simonii×P. nigra all aroused significant electrophysiological response of both sexes of X.rusticus.The behavioral test results further indicated that,the males and females exhibited attractive tendency to bark extraction of P.pseudo-simonii and P.simonii which have lower insect-resistant level,but showed repellent tendency to that of Populus×xiaozhuanica W.Y.Hsu et Liang cv.'Baicheng-2' and P.alba×P.berolinensis which have higher insect-resistance ability.Those experiment conclusions were identical with the actual X.rusticus damage status. At the same time,EAG tests were performed to six single compounds,2,6-ditertbutyl-4-methyl phenol,phenol,camphor,benzoic acid,1,3-dimethylbenzene and furfural at different concentration.Results showed that 2,6-ditertbutyl-4-methyl phenol had no function on adults of both sexes,furfural at 200μg dosage,the highest dosageused in the experiment,aroused distinct electrophysiological response.Simultaneously,it was found that the female and male adults have different sensitivity to different compounds at the same concentration.Through the investigation of copulation mechanism of X.rusticus,the non-contacted olfactory distinguishing did not play the leading role in the search for spouse of X.rusticus adults,the contacted sex pheromone was likely secreted from female adults.Using GC-EAD to test physiological activity of volatiles from larval frass,the component rouse electrophysiological response of male and female adults was primarily identified as heptane. But whether the heptane could disturb the behavior of X..rusticus adults in practice still needs to do a lot of study works subsequently to confirm.In phloem and xylem of trunk of ten poplar species with different insect-resistant level,at least nine phenolic acids was contined,which are benzoic acid,caffeic acid,chlorogenic acid, cinnamic acid,feruic acid,p-coumaric acid,sylicylic acid,syringic acid and vanillic acid.The content of vanillic acid was the highest in popar species with low resistance ability.However, the level of feruic acid,caffeic acid,cinnamic acid and p-coumaric acid was much higher in those resistance species than in the other species.The total amount of phenolic acids of P. simonii×P.nigra and P.berolinensis with high insect resistance was the highest.The changes of the enzyme activity of POD,SOD,GSH-ST and TChE in X.rusticus larvae fed on food containing those nine phenolic acids was determined.Results indicated that,eight phenolic acids,except benzoic acid,had significant inhibitory effect on TChE activity.This showed that TChE in larvae body was sensitive to polyphenols and those polyphenols can effectively inhibit this detoxifying enzyme in tested insect.The evidently inhibitory function to the enzyme activity of POD and GSH-ST was observed in chlorogenic acid,caffeic acid and syringic acid in the larval body.