Identification And Functional Analysis Of Aggregation Pheromones Of Thrips Tabaci And Host Volatiles Induced By T.tabaci

Thrips tabaci Lindeman is a serious pest in cotton production in Xinjiang,China.It is of great significance for agricultural production to take effective and environmentally-friendly measures to prevent and treat T.tabaci.To date,the aggregation pheromones and other active volatiles of several thrips species have been identified and successfully applied to monitoring and controlling thrips populations,however,the related research on T.tabaci has not been reported yet.In the present study,to identify and validate the aggregation pheromone of T.tabaci,we isolated and analyzed the main male-produced volatiles,and subsequently tested the behavior preference of males and females to each candidate.And then,we evaluated the effects of reported attractive compounds for other thrips on the selection behavior of T.tabaci.Finally,we isolated and identified the host plant volatiles induced by T.tabaci,and evaluated the behavioral selection of the main components on T.tabaci.The main results are as follows:1.Isolation,identification and behavior evaluation of putative aggregation pheromones of T.tabaciUsing a solid-phase micro-extraction device(SPME)and a gas chromatography-mass spectrometer(GC-MS),the main volatiles produced by male T.tabaci were isolated and identified as benzonitrile,nicotinamide and benzamide.The results of behavior test on a self-made two-choice tube showed that benzonitrile,nicotinamide and benzamide significantly attracted male T.tabaci at the concentration of 0.1 μg/μL,and attracted females at 0.1 μg/μL,0.01 μg/μL and 0.1 μg/μL respectively.The results also revealed that the attractiveness of the three volatiles positively increased with their concentrations.According to our results,it is preliminarily deduced that benzonitrile,nicotinamide and benzamide are the candidate aggregation pheromones produced from male T.tabaci.2.Assessment of the behavioral preference of T.tabaci to other thrips attractive compoundsEmploying the attraction index as evaluation index,the attractivenesses of 34 thrips-attractive compounds to T.tabaci females were determined on the olfactometer.The results showed that female T.tabaci could make effective choices to most thrips-attractive compounds.At the concentration of 0.001-0.02 μg/μL,γ-decanolactone displayed the best attractive activity,while2-phenylethyl acetate and methyl salicylate showed the best repellent activity.At the concentration of 0.1-10 μg/μL,2-methoxybenzaldehyde and methyl benzoate attracted most T.tabaci,while methyl salicylate had the best repellent effect.Consequently,γ-decanolactone,2-methoxybenzaldehyde and methyl benzoate were considered as the potential attractants for T.tabaci,meanwhile 2-phenylethyl acetate and methyl salicylate were screened as the candidate repellents.3.Effects of thrips-induced host plant volatiles on behavior of T.tabaciUsing SPME,coupled gas chromatography-electroantennographic detection(GC-EAD)and GC-MS,major components of host plant volatiles induced by T.tabaci were isolated,identified,and bioassayed on a self-made two-choice tube.The results showed that major volatiles collected from cotton(Gossypium spp)infested by T.tabaci were trans-2-hexenal and β-caryophyllene,meanwhile major volatile components released from thrips-infested Chinese onion(Allium fistulosum)were 2-undecanone and 2-tridecanone.Behavioral bioassays showed thatβ-caryophyllene significantly attracted both female and male T.tabaci at the concentration of 0.02μg/μL.Trans-2-hexenal significantly repelled adult T.tabaci at the concentration of 1 μg/μL.And the attracting and repelling effects showed significantly concentration-dependence.2-Undecanone and 2-tridecanone at the concentration of 0.1 μg/μL obviously repelled female T.tabaci.2-Undecanone at concentration of 0.02 μg/μL and 2-tridecanone at concentration of 0.1 μg/μL significantly repelled males.2-Undecanone at the concentration of 10 μg/μL and 2-Tridecanone at the concentration of 1 μg/μL obviously repelled nymphs.The repellent activites of two ketones positively increased with the concentrations.Based on our results,β-caryophyllene is a potential attractant for T.tabaci,while trans-2-hexenal,2-undecanone and 2-tridecanone are worth developing as potential repellents.