The Regulation Of Rice Volatiles On Intraspecific Interactions Of Anagrus Nilaparvatae

It has been documented that volatiles emitted from plants infested with parasitized herbivores by parasitoids are different from those from plants infested by herbivores.This difference influences the searching behavior of the parasitoid and thus regulates the intraspecific interaction of the parasitoid.Anagrus nilaparvatae is an important egg parasitoid of rice planthoppers.It has been reported that oviposition by the brown planthopper(BPH)Nilaparvata lugens elicits rice plants to produce volatiles and that these volatiles have a strong attractiveness to the egg parasitoid.However,whether the volatile profiling emitted from rice plants with BPH eggs will be altered when these BPH eggs are parasitized by the parasitoid and whether this change will influence the host searching behavior of the parasitoid remain unknown.Therefore,we here carried out such a research.The results are as follows:In a Y tube olfactometer bioassay,the parasitoid was found to be more attracted by volatiles emitted from rice plants with BPH eggs(PE)than those emitted from rice plants with BPH eggs that were parasitized by the parasitoid(PEP).Chemical analysis revealed that levels of four chemicals,MeSA,linalool,zingiberene and an unknown component in volatiles from PEP were significantly higher than those in volatiles emitted from PE.To determine whether these chemicals influence the behavioral response of the parasitoid,two synthetic chemicals,MeSA and linalool were respectively applied on PE and then investigated the behavioral response of the parasitoid to the two odors:volatiles from PE versus volatiles from PE plus one of the two synthetic chemicals.The result showed that volatiles from PE plus MeSA had a repellent role to the parasitoid,whereas volatiles from PE plus linalool had a tendency to attract the parasitoid.Chemical analysis found that application of MeSA on rice plants induced the production of other four chemicals,linalool,zingiberene,?-copaene and ?-bisabolene;and application of linalool elicited the production of MeSA in rice.Field experiments were conducted to evaluate the effect of these two compounds on the host searching behavior of the parasitoid.The results were similar to those found in the laboratory.These data suggest that BPH eggs-induced rice volatiles could be altered with the parasitization of BPH eggs by the parasitoid,which in turn influence the host searching behavior of the parasitoid.Among this process,the chemical,zingiberene,whose level increased when the BPH eggs were parasitized,might play an important role.