Behavioral Responses Of Sitobion Avenae To The Aphid Alarm Pheromone And Wheat Volatiles I Nduced By Aphid Feeding

Plants can release various volatiles which could possess a variety of ecological functions.Under attacks of herbivores, plants could emit a specific blend of volatiles, called herbivore-induced plant volatiles(HIPVs). HIPVs play a key role in plant-herbivore-enemy interactions. Feeding of Sitobion avenae(Farbricus) on wheat can also trigger specific emissions of volatiles which include 6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol and methyl salicylate. However, their specific functional roles remain unknown. Aphid alarm pheromones are another category of important semiochemical for aphids, and they can be released when aphids encounter their enemies. It has been reported that E?F is the only component of the alarm pheromone for S.avenae. Thus, whether there exist some interactions between aphid-induced wheat volatiles and the aphid alarm pheromone is an interesting question that remains unanswered. A series of chemical ecology techniques were used in experiments carried out to answer the questions described above. The results were as follows:1. There were apparent differences between the abundances and amounts of volatiles from healthy and aphid infected wheat seedlings. Only the relative quantity of 3-ethyl-1,5-octadiene declined significantly among all the volatiles from aphid infected wheat seedlings,little variation was found for other volatiles. Compared with that in healthy wheat seedlings,no o-Cymene was detected in the volatile profile of aphid infected wheat seedlings, and(Z)-7-Hexadecene and(E)-?-farnesene were new components. According to previous studies on functions of wheat terpene synthease gene,(E)-?-farnesene may repel aphids.2. The concentration with the best repellent effects for the above mentioned semiochemicals was 100, 1, 1, and 10 ng/?L, respectively. All mixtures of two or three wheat volatiles reduced the repellent effect on S.avenae compared to single volatile treatments.Compared to E?F, the mixture of methyl salicylate or 6-methyl-5-hepten-2-ol with E?F reduced the repellent effects of E?F. However, the mixture of 6-methyl-5-hepten-2-one with E?F still showed strong repellent effects.3. Wing dimorphism experiments showed that E?F alone increased the proportions of S.avenae's winged offspring, and the inductive effects seemed to last for three generations.And the mixture of the two compounds could not. 6-methyl-5-hepten-2-ol might increase the percentage of S.avenae? s winged offspring, but the result not significant compared with control.All of the results suggested that 6-methyl-5-hepten-2-ol might inhibit the perception of E?F by S.avenae.