Potential Effects Of Imidaclothiz And Chlorpyrifos On The Dominant Parasitoid Of Binodoxys Communis

Aphis gossypii is a major pest of cotton fields worldwide.It damages cotton plants by sucking juice and transmitting toxins,which seriously damages the economic value of cotton.At present,chemical pesticides are important means to control cotton aphids,but long-term use of chemical pesticides will cause certain harm to natural enemies in cotton fields.Binodoxys communis is the dominant parasitic natural enemy of A.gossypii,which can reduce the population of A.gossypii naturally and effectively,and has great application prospect of biological control.Imidaclothiz and chlorpyrifos are two new and commonly used insecticides in cotton fields in China.However,the potential effects of sublethal doses of imidaclothiz and chlorpyrifos on the parasitoid B.communis have not been studied.The purpose of this study was to clarify the sublethal and intergenerational effects of imidaclothiz and chlorpyrifos on B.communis,and to analyze the changes of gene expression level of B.communis by transcriptomics,so as to scientifically and effectively guide the combination of chemical control and biological control,and lay a theoretical foundation for the protection of natural enemies and the rational and safe use of insecticides in the field.The main results are as follows:1.Indoor toxicity of imidaclothiz and chlorpyrifos to B.communis.The acute toxicity of imidaclothiz and chlorpyrifos to B.communis was determined by the drug film method.The results showed that the toxicity of imidaclothiz to B.communis was low(LC₅₀:52.01 mg/L;LC₃₀:28.03 mg/L;LC₁₀:11.48 mg/L).The LC₁₀,LC₃₀and LC₅₀of chlorpyrifos were 1.88 mg/L,4.69 mg/L and 8.83 mg/L,respectively.2.Sublethal effects of imidaclothiz and chlorpyrifos on B.communis.The effects of sublethal concentrations of imidaclothiz and chlorpyrifos on B.communis were determined.The results showed that the survival rate,parasitism rate,eclosion rate and adult survival time of F₀generation of B.communis were significantly reduced by LC₃₀of imidaclothiz,and LC₁₀concentration had no significant effect on these biological indicators.Both LC₁₀and LC₃₀concentrations of imidaclothiz significantly prolonged the egg-larvae development duration of the F₀generation.In addition,LC₁₀concentration of imidaclothiz significantly shortened the pupal stage of the F₀generation.In the chlorpyrifos treatment group,only LC₁₀concentration had a significant negative effect on the emergence rate and larval development duration of the F₀generation of B.communis.Interestingly,imidaclothiz and chlorpyrifos showed a continuous cross-generation effect on B.communis.The survival rate,offspring survival time and egg-larval stage of F₁generation of B.communis were significantly decreased,and the pupal stage was significantly prolonged after treatment with chlorothiine at LC₁₀concentration.The survival rate and eclosion rate of F₁generation of B.communis were significantly reduced by the concentration of imidaclothiz at LC₃₀.Both concentrations of chlorpyrifos significantly reduced the survival rate and emergence rate of F₁generation,shortened the survival time and egg-larvae development duration of F₁generation.However,neither imidaclothiz nor chlorpyrifos had adverse effects on the parasitism rate of the F₁generation of B.communis.3.Effects of imidaclothiz and chlorpyrifos on the gene transcription level of B.communis.In order to further study the potential effects of imidaclothiz and chlorpyrifos on B.communis,high-throughput transcriptome analysis was performed on samples treated with CK-1h,Im LC₁₀-1h,Im LC₃₀-1h,Dsp LC₁₀-1h,Dsp LC₃₀-1h,CK-3d,Im LC₁₀-3d,Im LC₃₀-3d,Dsp LC₁₀-3d and Dsp LC₃₀-3d.The results showed that 5562 and 4275differentially expressed genes were obtained after 1 h treatment with LC₁₀and LC₃₀,and22 and 1045 differentially expressed genes were obtained after 3 d treatment.After treatment with chlorpyrifos,3717,2382,32 and 14 differential genes were obtained,respectively.The number of differential genes treated with two pesticides at different times indicated that the expression of most differential genes may return to normal levels through self-regulation in long-term sublethal pesticide exposure.After KEGG pathway enrichment,the differential genes were mainly enriched in heat production,oxidative phosphorylation,ribosome,PPAR signaling pathway,glutathione metabolism,drug metabolism-cytochrome P450,m TOR and some basic energy metabolism pathways.Among them,the PPAR signaling pathway was significantly enriched between the treatment groups of imidaclothiz and chlorpyrifos.The key genes of PPAR signaling pathway（UBC,HNGCS2,APO-C3,CPT1A,ACADL,APOA1-1,APOA1-2）were verified by real-time quantitative PCR,which was consistent with the trend of transcriptome results,indicating that sublethal doses of imidaclothiz and chlorpyrifos may affect the downstream fatty acid-related metabolic pathways by inhibiting the expression of PPAR signaling pathway genes,resulting in the disorder of growth and reproductive regulation of B.communis.In summary,the sublethal effects of imidaclothiz and chlorpyrifos may be related to the PPAR signaling pathway.In this study,the sublethal and intergenerational effects of imidaclothiz and chlorpyrifos on B.communis were clarified,and the effects of imidaclothiz and chlorpyrifos on the biological indexes of the experimental population of B.communis were clarified.The effects of these two pesticides on the gene transcription level of B.communis were analyzed,which laid a foundation for revealing the molecular mechanism of the effects of imidaclothiz and chlorpyrifos on B.communis.The results of this study highlighted the possible unintended sublethal and intergenerational effects of imidaclothiz and chlorpyrifos on the dominant parasitoid B.communis,which is of great significance for the comprehensive control of cotton aphids.