| In the long-term of natural evolution,behaviors form a biological rhythm under an oscillatory environment of a roughly 24 h cycle in most organisms.Studies indicated that the release of volatiles,especially herbivore-induced plant volatiles,forms a 24 h cycle,and the timing of release can affect the function of each compound.Our previous work indicated that rice plants damaged by Chilo suppressalis attracted Cotesia chilonis,but repelled its mated females.So,which key compounds are released rhythmic in rice to defense with C.suppressalis larvae? In this study,the diurnal release rhythms of key volatiles were systematically analyzed in rice infested by C.suppressalis,and the effects of these volatiles on selection behavior of C.suppressalis mated females and C.chilonis were explored,finally the relationship between the rhythmic release of these key volatiles and the defense response of rice to the pest of the borer was verified.Detailed results are following:(1)22 compounds were identified in healthy rice and 8 new compounds were obtained in C.suppressalis infested rice plants through dynamic headspace collection system and GC-MS analysis.In the daytime,8 more compounds were released from infested rice plants than healthy rice.While in the night,10 more volatiles were released from infested rice.Among the 22 common volatiles,14 volatiles released from infested rice were much more than healthy rice.However,in healthy rice,only acetylbenzene released significantly higher than in damaged rice at night.Among the 30 volatiles in infested rice,the peak of 22 volatiles release was at 12:00 am to 3:00 pm,the peak emission of two volatiles was at 9:00 am to 12:00 am,and one volatile peaked from 3:00 pm to 9:00 pm.Among these volatiles,only 8 compounds had the same peak as the healthy rice.In other words,the rice damaged by C.suppressalis not only changed the compositions and release amounts of volatiles,but also affected their diurnal release rhythms.(2)Compared with healthy rice,20 compounds released significantly in the daytime.These compounds from infested rice were verified their effects on host selection of parasitoids by Y-tube olfactometer.Results showed that linalool,isophorone,trans-2-heptenyl acetate,α-pinene(10 ng/10 μL)and 2-heptanol(100 ng/10 μL)attracted parasitoids.Except for isophorone,the peak emission of these compounds was at 12 am to 3 pm,which is overlapped with the activity peak of C.chilonis.(3)In wind tunnel experiments,seven compounds were chosen to test their effects on the selective behavior of mated C.suppressalis moths.Results showed that 2-nonanone,isophorone,methyl salicylate and trans-2-heptenyl acetate repelled female moths.The diurnal release rhythm of these volatiles was not consistent with the active time of adults,and the related mechanism needs to be further studied.In summary,this study drawn the rhythm pattern of C.suppressalis damage induced the release of volatiles.And the diurnal release rhythms of specific key volatiles affecting the selective behavior of female moth and parasitoids were proofed,which provided scientific support for developing technology for C.suppressalis control.What’s more,a new perspective was found to clarify the evolutionary mechanism in plant-herbivore-enemy. |
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