Effect Of Volatile Metabolites Emitting From Leaves Of Salix Suchowensis And Salix Triandra On Host Selection For Plagiodera Versicolora And Identification Of The Functional Chemicals

For relationship between host plants and herbivores,how herbivore find the host is the key interaction.This study investigate the host finding of willow beetle,Plagiodera versicolora for two different willows.It was found that infestation of willow beetles was severe on germplasm collections of Salix suchowensis,while were intact on collections of Salix triandra through years of empirical observation.Thus,it is an intriguing question how the beetles discriminate different willow hosts.Experiments in this study showed that Salix suchowensis is a host plant,while Salix triandra is highly resistant to this beetle.Using leaves of Salix suchowensis and Salix triandra,visual and olfactory response tests were conducted for adult Plagiodera versicolora.Subsequently,the headspace volatile organic compounds were profiled with solid-phase micro extraction gas chromatography-mass spectrometry.On this basis,effect of 23 chemical analogs was examined on host discrimination of the beetles.The main results are as follows:1.Damage level and feeding rate were taken into account to figure out which willow is preferred by adult Plagiodera versicolora.Salix suchowensis is identified as a host plant because it is slightly damaged with feeding rate of 37.1% ± 6.2%.By contrast,Salix triandra is a non-host because it is severely damaged with feeding rate of 0%.2.Through visual and olfactory bioassays,we found that visual signals of Salix suchowensis and Salix triandra are the stimuli of the beetles.However,results of olfactometer bioassays showed that the headspace volatiles from leaves of Salix triandra had significant effect to repel the adult beetles,suggesting that this willow might produce volatile repellents against.3.Analyzing the metabolites emitting from leaves of the two willow species detected a total of 23 compounds with relative abundance ?0.5%.Among which,20 of them were known chemicals,and 22 compounds showed significant difference in quantity(P <0.05).4.A total of 23 treatments were set up with 15 compounds,and tests indicated that the repellent volatile from leaves Salix triandra is cis-3-hexenyl acetate with leaves/h emission of 1796.69 ng/g.While attractant volatile from leaves of Salix suchowensis o-cyneme with leaves/h emission of 293.05 ng/g.However,its effect was masked by cis-3-hexenyl acetate with leaves/h emission of 290.62 ng/g.5.This study detected two volatile metabolites had significant effect on host discrimination for adult Plagiodera versicolora.The two metabolites are of great potential to be used as olfactory cues in managing the beetles.In summary,this study detected that o-cymene emitting from leaves of Salix suchowensis is a species-specific constituent that had significant attractive effect to adult Plagiodera versicolora,while cis-3-hexenyl acetate is a repellent to adult beetles.This constituent is condensed over five-folds in volatiles of Salix triandra than that of Salix suchowensis.