Regulations Of Beauveria Bassiana On Oviposition Selection Of Ostrinia Furnacalis

Plants and insects are two important components of terrestrial ecosystems,and interact to form complex relationships during the long-term evolution.Plants provide food resources for insects and spawning sites.Therefore,host selection behavior of insects has important effects on their growth and development and the reproduction.Oviposition is a central stage in the life history of insects,and it is directly related to their population size.The insect host selection behavior has become one of hot issues for entomologist and behavior researchers.Plant volatiles have crucial roles in mediating insect oviposition selection behavior.Identifying and utilizing plant volatiles becomes an important means of pest biocontrol during oviposition.The Asian corn borer(ACB),Ostrinia furnacalis Guenée(Lepidoptera: Crambidae),is one of the most serious insect pests of maize(Zea mays)in China.Until now,Beauveria bassiana is a common tool for controlling ACB.Beauveria bassiana is an insect pathogenic fungi,and recent research showed that B.bassiana could colonize into plants as endophytes that have been shown to increase plant resistance,promote plant growth.Thus,B.bassiana may mediate plant volatile,and consequently influencing oviposition host selection of insects.In this study,from the perspective of chemical ecology,maize leaf volatiles were analyzed for identifying the main component that attract ACB during oviposition,which has important theoretical significance for effective reduction of Asian corn borer population and scientific biological control.Meanwhile,the effect of B.bassiana on the oviposition selection of ACB was explored.It provided a theoretical basis for revealing the microbe-insect interaction,and provide new insight into controlling ACB biologically.In this study,solid phase micro-extraction(SPME)technology and dynamic headspace adsorption method were used to extract volatiles from maize leaves.,and the composition and content of main volatile components in maize leaves were determined by gas chromatography-mass spectrometry(GC-MS).Then,the responses of ACB to leaf volatile of maize were analyzed by using of insect antennae potential technology(EAG),and were further tested through oviposition bioassay.The effects of B.bassiana on oviposition selection of ACB was analyzed in four B.bassiana strains treatments(Control,A3,A8,and D1-5),and pathway on B.bassiana effects on oviposition of insects were analyzed by comparing the difference of volatiles and nutrients in maize leaves.The main conclusions of this study were as follows:1?The result suggests showed that 31 species of volatiles were identified by SPME and dynamic headspace adsorption method.Among them,27 species were determined by SPME,and17 compounds were as main components,including ?-caryophyllene,cis-3-hexenol,hex-anol,2-ethylhexanol,trans-2-hexenal,cis-3-hexenal,acetate ethoxylate,1,3-dimethylbenzene,undecane,dodecane,pentadecane,hexadecane,heptadecane,octadecane,nonadecane,eicosane and naphthalene.The content of ?-caryophyllene and 2-ethylhexanol were the higher,accounting for 14.99% and 7.69% respectively.5 components were obtained by dynamic headspace adsorption method,including ?-pinene,limonene,1,3-dichlorobenzene,1,3-dimethylbenzene,and naphthalene,naphthalene and ?-pinene were the higher,accounting for 45.73% and 27.40% respectively.2?Combining most previous studies and this study,twenty-six compounds from maize leaves were selected for EAG.Results showed that there were differences among different plant volatiles when these components affected female Ostrinia furnacalis,and the sensitivities of O.furnacalis to eleven compounds,including ?-ocimene,?-pinene,linalool,trans-2-hexenal,cis-3-hexenol,2-ethylhexanol,naphthalene,?-caryophyllene,octadecane,eicosane,dodecane,were higher.Thus,these eleven compounds were selected to further tested through oviposition bioassay experiments.Results showed that ?-ocimene,cis-3-hexenol,2-ethylhexanol attracted oviposition of the gravid female,but ?-pinene,?-caryophyllene,trans-2-hexenal,naphthalene prohibited oviposition of the gravid female,and linalool,octadecane,eicosane,dodecane had no effects.3?By examining the oviposition changes of Ostrinia furnacalis in the treatments with different B.bassiana strains,egg masses and egg numbers in A3 treatment were significantly higher than those of control,A8,and D1-5.This suggests that Ostrinia furnacalis prefer to lay eggs on plants that colonized by A3 strain.4?Results from this study showed that the content of cis-3-hexenol,2-ethylhexanol that could attract the gravid female ovipositing increased,whereas the content of ?-caryophyllene and naphthalene that prohibit the gravid female ovipositing decreased in A3 treatments.However,the contents of C and N were not significantly different among all treatments.Therefore,it indicates that A3 B.bassiana affects the oviposition choice of Asian corn borer by changing the content of volatiles in maize leaves.To sum up,on the one hand,this study identified the main component of maize leaves that attract or prohibit the oviposition of ACB,which have an important role in recognized the interaction between plant-herbivore interactions.And moreover,the regulations of B.bassiana on the oviposition choice of ACB provides a theoretical basis for a deep understanding of the interactions between microbe and insects,and lend a new insight into controlling pests biologically.