Regulation Of Neighbor Relationship Between Maize And Soybean On Oviposition Behavior Of Ostrinia Furnacalis

In most ecosystems,plants often display neighborhood relationships with conspecific or other plant species,the neighborhood relations have been shown to affect the growth and population size of herbivorous insects by associational effects,including associational resistance and associational susceptibility.However,how the associational neighborhood relation among plants alters the oviposition behavior of herbivorous insects needs to be further explored.Recently,plant volatiles profiles have been focused because it is considered as one of the important ways for driving oviposition selection of insects.However,the knowledge on the effects of plant neighbor relationships on insect oviposition behavior has not been clearly understood from a perspective of volatile compounds.In this study,two important crops,maize(Zea Mays)and soybean(Glycine Max)were selected as tested plants to compare the difference in oviposition of Ostrinia furnacalis for target maize plants under different neighbor relationships in greenhouse.The emission of volatile compounds from maize and soybean plants was measured by solid-phase microextraction(SMPE)and gas chromatography mass spectrometry(GC-MS).The responses of O.furnacalis oviposition selection to main volatiles of the tested plants were tested through EAG and bioassay experiments,and analyzed possible mechanisms on the effects of neighboring relationships between maize and soybean on oviposition behavior of O.furnacalis.1.The number of eggs laid by O.furnacalis on maize plants adjacent to soybean was significantly lower than that adjacent to conspecific plants.The number of egg masses and eggs on maize plants with 30 cm distance from soybean were significantly lower than those with 90 cm distance from soybean.2.A total of 28 volatile compounds,including 7 categories(hydrocarbon,alcohol,aldehyde,ester,fatty acid,ketone and terpene)were detected from the leaves of soybean plants.There were less volatile species(25 species)in the leaves of target maize plants adjacent to soybean,and the relative contents of hexanal,pentadecane,(Z,E)-farnesol and pentadecanoic acid were significantly different,compared with the maize plants whose neighbor was conspecific individuals.3.The results from electroantennography experiment showed that the relative EAG response values of O.furnacalis to most of the compounds at 1000 ppm was higher,compared to 10 and 100 ppm,and the relative EAG response values to naphthalene,3-octanone,1-hexanol,1-octanol,3-octanol,2-ethylhexanol,benzyl alcohol,1-octene-3-ol,(Z)-3-hexen-1-ol,linalool,decanal,nonanal,4-pentenal,(E)-2-pentenal,(E)-2-pexenal,(E)-2-heptenal,(E)-2-octenal and(E,E)-2,4-hexadienal were relatively higher.Further oviposition bioassay showed that naphthalene,decanal,3-octanol,4-pentenal and(E)-2-hexenal had significant repellent effects on the oviposition selection of O.furnacalis.Additionally,the relative EAG value of O.furnacalis to hexanal emitted from the target maize leaf was higher,but hexanal had no significant effect on the oviposition selection of O.furnacalis.In conclusion,under greenhouse conditions,the neighboring relationships between maize and soybean can produce associational resistance to oviposition behavior of O.furnacalis,and effectively reduce the number of eggs laid by O.furnacalis on the maize plant.This was mainly because naphthalene,decanal,3-octanol,4-pentenal and(E)-2-hexenal emitted from soybean had a significant repellent effects on the oviposition behavior of O.furnacalis.This study not only enriches ecological theory on the regulation of plant diversity for insect pests in agricultural ecosystems from the perspective of chemical ecology,but also provides theoretical support for monitoring the population dynamics of O.furnacalis during maize and soybean intercropping,and has practical guiding significance for the scientific and effective biological control for O.furnacalis.