| The Chinese rice grasshopper Oxya chinensis(Orthoptera:Acridoidea) widely and abundantly distributes in most regions of China.This grasshopper species represents an important agricultural pest to rice and other gramineous crops.Traditionally,chemical control has been a major method for protecting rice from damage by Oxya chinensis and is likely to remain an important component of control strategies for the foreseeable future.This study examined the relationship of allozyme genotype and the differential acute mortality of in Oxya chinensis collected from Jinyuan District,Taiyuan, Shanxi province to four commonly used pesticides(Phoxim,Chlorpyrifos, acephate,methomyl).The interaction of genotype and toxic effects of pesticides was explored to the possible applications as potential biomarker so as to inspect resistance dynamics and to obtain may also be useful in pesticide application assessment for reasonable use,efficiency improvement and for decreasing the toxicity to non-target organisms in grasshopper control programs.Insect resistance to pesticides is evolutionary event;possibly form the genetic structure alternations within a population under the constant directional selection by pesticides.The allozyme analysis technique turns out to be of technical ease,quick and low in cost.It is possible to simultaneously assay a lager amount of samples at many loci and many alleles in a short period of time using horizontal starch gel eletrophoresis.Thus the allozyme analysis technique can quickly estimate population genetic structure and dynamic changes of population genetic structure so as to provide a new idea for the inspecting indices and evaluating basis of pest resistance to pesticides. This dissertation compared the differential acute mortality using allozyme analysis technique among the allozyme genotypes of polymorphic loci of the grasshopper after treatment with four pesticides(Phoxim,Chlorpyrifos, acephate,methomyl).The grasshopper O.chinensis exhibits high polymorphic loci at Mdh-1,Ldh,Me,Pgi and Pgm.the allozyme analysis was employed to determine the genotypes frequency for both dead and surviving individuals. Contingency tableχ~2 tests showed the differential genotypic effects on the mortalities of O.chinensis at certain polymorphic loci depending on the pesticide.A total of 394 O.chinensis individuals from Jinyuan District were exposed to phoxim(1.96μg/g) to obtain a mortality of 49.2%after 24 hours. The allozyme analysis was then employed to determine the number of each genotype for both surviving and dead individuals.The differential mortality among the allozyme genotypes of O.chinensis was compared between surviving and dead groups of the grasshopper.Contingency tableχ~2 tests showed that Phoxim displayed random lethal effects on the genotypes at the loci of Ldh,Pgm,Mdh-1 and Me,without evident correlation between the genotype and mortality.In contrast,at Pgi locus,the grasshopper demonstrated a mortality order of Pgi-BB(30%),Pgi-AA(46%), Pgi-AB(61%).The significant mortality differences were found between Pgi-BB and Pgi-AB,These data implies the Pgi-BB genotype is likely related to the resistance of O.chinensis to the pesticide Phoxim.A total of 404 O.chinensis individuals from Jinyuan District were exposed to Chlorpyrifos(3.69μg/g) to obtain a mortality of 51.7%after 24 hours.The allozyme analysis was then employed to determine the number of each genotype for both surviving and dead individuals.The differential mortality among the allozyme genotypes of O.chinensis was compared between surviving and dead groups of the grasshopper.Contingency tableχ~2 tests showed that Chlorpyrifos displayed random lethal effects on the genotypes at the loci of Ldh,Me and Pgi,without evident correlation between the genotype and mortality.In contrast,at Mdh-1 locus,the grasshopper demonstrated a mortality order of 31%(Mdh-1-AB),49%(Mdh-1-BB)和64%(Mdh-1-BC),The significant mortality differences were found between Mdh-1-AB and Mdh-1-BB,Mdh-1-BC.at Pgm locus,The significant mortality differences were found between Pgm-AB and Pgm-BC,These data implies the Mdh-1-AB and Pgm-AB genotype are likely related to the resistance of O.chinensis to the pesticide Chlorpyrifos.A total of 478 O.chinensis individuals from Jinyuan District were exposed to acephate(13.1μg/g) to obtain a mortality of 47.9%after 24 hours. The allozyme analysis was then employed to determine the number of each genotype for both surviving and dead individuals.The differential mortality among the allozyme genotypes of O.chinensis was compared between surviving and dead groups of the grasshopper.Contingency tableχ~2 tests showed that acephate displayed random lethal effects on the genotypes at the loci of Ldh,Pgm,Mdh-1 and Me,without evident correlation between the genotype and mortality.In contrast,at Pgi locus,the grasshopper demonstrated a mortality order of Pgi-BB(40%),Pgi-AA(42%), Pgi-AB(56%).The significant mortality differences were found between Pgi-BB and Pgi-AB,These data implies the Pgi-BB genotype is likely related to the resistance of O.chinensis to the pesticide acephate.A total of 367 O.chinensis individuals from Jinyuan District were exposed to methomyl(4.69μg/g) to obtain a mortality of 45.0%after 24 hours.The allozyme analysis was then employed to determine the number of each genotype for both surviving and dead individuals.The differential mortality among the allozyme genotypes of O.chinensis was compared between surviving and dead groups of the grasshopper.Contingency tableχ~2 tests showed that methomyl displayed random lethal effects on the genotypes at the loci of Ldh,Pgm,Mdh-1 and Me,without evident correlation between the genotype and mortality.In contrast,at Pgi locus,the grasshopper demonstrated a mortality order of Pgi-BB(20%),Pgi-AA(35%), Pgi-AB(55%).The significant mortality differences were found between Pgi-BB and Pgi-AB,These data implies the Pgi-BB genotype is likely related to the resistance of O.chinensis to the pesticide methomyl.
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