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Effect Of Bacillus Thuringiensis And Abamectin Biopesticide Mixture On Sex Pheromone Communication System In Cotton Bollworm, Helicoverpa Armigera

Posted on:2014-06-30Degree:MasterType:Thesis
Country:ChinaCandidate:L Z ShenFull Text:PDF
GTID:2253330425951926Subject:Forest Protection
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Consumption of Bacillus thuringiensis and Abamectin (BtA) biopesticide mixture is increasingannually. However, abuse of BtA is a serious problem and can actually increase risk via pesticide residuein fields and inducing high pesticide resistance and imperilling natural enemies. In this study, we justinitiated using cotton bollworm, Helicoverpa armigera, as a model organism to evaluate the sublethaleffect of larvae treated with mixed biopesticide BtA on the moth sex pheromone communication systemand other reproductive behaviors. We expect the progress we make in understanding H.armigera will alsotranslate to anticipating, addressing and resolving problems that arise with other lepidopterans as relianceon GMO technologies continues. How BtA affects H.armigera could point us to a course of action thatmay include using a new ratio of lure, a more suitable dose of pesticide in the field, etc. to accommodatethese changed reproductive behaviors. Our thesis consists of two parts:1. Sublethal effect of3rdlarvaetreated with mixed biopesticide BtA on moth sex pheromone communication system;2. Bioinformaticsanalysis and Homology modelling of pheromone biosynthesis activating neuropeptide receptor ofHelicoverpa arimigera (HarmPBANr) by threading method and predicting extracellular putative bindingsites of HarmPBANr.1. Sublethal effect of3rdlarvae treated with mixed biopesticide BtA on moth sex pheromonecommunication system:(1) After3rdlarvae treated with sublethal dose of BtA, mortality of3rdlarvae, malformed pupal rate andpupal stage were decreased as concentration of BtA increasing. On the contrary, pupation rate andeclosion rate were increased. Interestingly, mean pupal weight of males was decreased while meanpupal weight of females was increased as BtA concentration increasing.(2) After3rdlarvae treated with sublethal dose of BtA, calling rhythm or periodicity of calling of adultsurvived females was similar but calling rate was lower than control females. The adult survivedfemales produced higher sex pheromone titers but ratio of Z-11-hexadecenal (Z11-16:Ald) and Z-9-hexadecenal (Z9-16:Ald) changed and coefficients of variation (CV) of Z11-16:Ald and Z9-16:Aldwere expanded compared to control females.(3) After3rdlarvae treated with sublethal dose of BtA, the adult male survivors showed higherelectroantennography (EAG) responses to Z11-16:Ald, Z9-16:Ald and the97:3blend of Z11-16:Ald and Z9-16:Ald than control males. In the wind tunnel bioassay, the BtA-treated males exhibited ahigher percentage of "orientation" than control males but lower percentages of "approaching" and"landing".(4) In mating choice experiment, both control males and BtA-treated males preferred to mate withcontrol females and a portion of the Bt-A treated males did not mate whereas all control males did.2. Bioinformatics analysis and Homology modelling of pheromone biosynthesis activatingneuropeptide receptor of HarmPBANr:The3D model of HarmPBANr was built using the crystal structure of bovine rhodopsin (PDB:1u19)as threading method of homology modelling. Seven transmembrane regions of HarmPBANr fit the1u19template very well, while there are some differences between the model and the template at the N-terminus,intracellular loops and extracellular loops. Extracellular putative binding sites of HarmPBANr are Thr24,His26, Gln33, Glu110, Ile114, Met177, Gln178, Ile181, Ser183, Tyr184, Lys197, Leu296, Tyr307, Ile308,and Val309.
Keywords/Search Tags:Helicoverpa armigera, Bacillus thuringiensis, Abamectin, Sex Pheromone, Wind Tunnel, Electroantennogram (EAG), Mating Choice, ReceptorProtein, Homology Modelling
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