Research Of Volatile Compounds Of Rubber Tree And Its Behavioral Activities On Two Species Of Bark Beetles

Natural rubber plays an important role in national defense and economic construction which is a strategic material in China.Bark beetles are important borer pests that causes serious damage to rubber trees,because they have the characteristics of strong reproductive ability,wide adaptability,strong individual concealment,strong drug resistance,etc.which is difficult to control and easy to form large-scale explosive disasters.In recent years,bark beetles have become more and more harmful to rubber forests,causing serious economic losses.Xyleborus affinis Eichh and Euplatypus par allelus are the dominant species of rubber trees.In order to investigate whether the volatile substances in rubber trees have a tendency to the olfactory behavior of Xyleborus affinis and Euplatypus parallelus,determine attractive volatile substances.The volatile components of gum trees were extracted by solid phase microextraction(SPME)and identified by gas chromatography-mass spectrometry(GC-MS).The electrophysiological responses and Y-tube olfactometer were used to study the behavioural of Xyleborus affinis and Euplatypus parallelus.The results are as follows:1.The peak retention time of rubber tree volatile gas in GC-MS chromatogram was 2-36 min.27 components were identified,including 10 paraffins,3 amines,2 dilute,5 esters,2 benzene,and 1 aldehyde,acid,ketone,phenol and alcohol.2.The results of electrophysiological and olfactory behavioral tests on the volatile components of rubber trees of Xyleborus affinis and Euplatypus parallelus showed that p-cymene,longifolene,tetradecane and 2-phenyl-2-propanol had a attraction effect on both bark beetles.Diphenyl phthalate(2-ethyl-hexyl),diethyl phthalate,methyl palmitate,2,6-ditert-butyl-4-methyl phenol were found to have a repellent effect on both bark beetles.The five compounds dibutyl phthalate,undecane,acetophenone,3-ethylbenzaldehyde and n-hexadecane showed no significant trend.Therefore,p-cymene,longifolene,tetradecane and 2-phenyl-2-propanol were selected as the composition of four compounds for the dose response test.3.The results of electrophysiological and olfactory behavior concentrations tests on the volatile components of rubber trees of Xyleborus affinis and Euplatypus parallelus showed that longifolene has the best attraction effect to Xyleborus affinis under the concentration of 0.10mg/mL,the selectivity coefficient was 0.1979±0.12.When the concentration of 1.00mgml-1,the selectivity coefficient was 0.3066±0.15,which has the best attraction effect to Euplatypus parallelus.Both species of bark beetles had the best attraction effect when the p-cymene mass concentration was 0.10mg/mL,the tetradecane mass concentration was 1.00mg/mL and the 2-phenyl-2-propanol mass concentration was 100mg/mL.4.Eleven kinds of compounds numbered 1-11 mixed by using p-cymene,longifolene,tetradecane and 2-phenyl-2-propanol in a volume ratio of 1:1 all have an attracting effect on Xyleborus affinis and Euplatypus parallelus.The compounds of different combinations have different attracting effects on Xyleborus afffinis than the single compound.The attractant effect of p-cymene and longifolene mixture,longifolene and 2-phenyl-2-propanol mixture is stronger than that of single compound,showing synergistic effect;The attractant effect of p-cymene and longifolene mixture,longifolene and 2-phenyl-2-propanol mixture is stronger than single compound,showing synergistic effect;The attractant effect of p-cymene and tetradecane mixture,longifolene and tetradecane mixture,tetradecane and 2-phenyl-2-propanol mixture are not different from single compound;The attractant effect of p-cymene and 2-phenyl-2-propanol mixture is slightly lower than single compound,showing antagonistic effect.Compared with the single compound,the mixed compound of different combinations also has different attraction effect on Euplatypus parallelus.P-cymene and longifolene mixture,longifolene and 2-phenyl-2-propanol mixture which have the attraction effect is stronger than that of the single compound have synergistic effect;P-cymene and tetradecane mixture,longifolene and tetradecane mixture,tetradecane and 2-phenyl-2-propanol mixture,P-cymene and 2-phenyl-2-propanol mixture is not significantly different from those of single compounds.In conclusion,the same mixed compound component may have different effects on both bark beetles,for example,p-cymene and 2-phenyl-2-propanol mixture has antagonistic effect on Xyleborus afinis,but has no significant effect on Euplatypus parallelus.In the olfactory behavior reaction of Xyleborus afinis had the strongest tendency to longifolene and 2-phenyl-2-propanol mixture,but its EAG value was not the largest in the electrophysiological test.In addition,in the olfactory behavior of Euplatypus parallelus,it had the strongest tendency to p-cymene and longifolene mixture,and the EAG value was the largest in the electrophysiological test.