Evaluation Of Sublethal And Transgenerational Effects Of Pesticide On Aphis Gossypii Via Life Table Parameters And 16s RRNA Sequencing

Aphis gossypii,a typical polyphagous and recurrent pest,causes tremendous loss in the yield of crops each year.Insecticide-induced hormesis is one of the key pathways for the development of cotton aphid resistance,previous studies of pesticide-induced sublethal effects mechanism mainly focus on gene level.The symbiotic bacteria are also important participants of this mechanism,but their roles in hormesis are still unclear.In this study,life table parameters and 16S r RNA sequencing were applied to evaluate the sublethal and transgenerational effects of two pesticides（sulfoxaflor,deltamethrin）on adult A.gossypii after 24 h exposure,and the relationship between insecticides and symbiotic bacteria was also studied,mainly have the following conclusions:1 Determination of susceptibility of A.gossypii to sulfoxaflor and deltamethrin（1）Toxicity of sulfoxaflor to A.gossypii.The LC₅₀ value of sulfoxaflor was calculated as 24.95 mg/L with a confidence interval of 14.25–49.53 mg/L and the LC₉₅ value was calculated as 302.54 mg/L with a confidence interval of 125.10–1409.37 mg/L.The LC₂₀ value of sulfoxaflor was calculated as 6.96 mg/L with lower and upper limit of 3.43 and 12.20 mg/L,respectively.The obtained LC₂₀ value was used as the sublethal concentration for evaluating the sublethal effect of sulfoxaflor on cotton aphid in the subsequent experiments.（2）Toxicity of deltamethrin to A.gossypii.the LC₁₀,LC₃₀ and LC₅₀ of deltamethrin to A.gossypii were 9.13,39.88 and 110.74 mg/L,respectively.The LC₃₀ value of deltamethrin was used as the sublethal concentration in the next experiment.2 Sublethal effects of sulfoxaflor and deltamethrin on parent generation and transgeneration population of A.gossypii（1）The effects of sulfoxaflor on the population parameters in parent generation and transgenerational population of A.gossypii.The results indicated that the LC₂₀ of sulfoxaflor significantly reduced the finite rate of increase（λ）and net reproductive rate（R₀）of parent generation（G0）,and significantly increased mean generation time（T）of G1 and G2,but not of G3 and G4.Both reproductive period and fecundity of G1 and G2 were significantly higher than those of the control.（2）The effects of deltamethrin on the population parameters in parent generation and transgenerational population of A.gossypii.The sublethal concentration of deltamethrin(LC₃₀)had no significant effect on the longevity and fecundity of the directly exposed aphids,but significantly decreased by intrinsic rate of increase（r）and finite rate of increase（λ）.Besides,the sublethal concentration stimulated the fecundity of the adult in the offspring（G1 and G2）,but did not observed in G3 and G4.3 The effects of sulfoxaflor and deltamethrin on the symbiotic bacteria in parent generation and transgenerational population of A.gossypii（1）Effects of sulfoxaflor stress on the symbiotic bacterial community of in three successive generations of A.gossypii.Our sequencing data revealed that more than 95%of bacterial communities were made up of Proteobacteria,in which the maximum proportion genera was the primary symbiont Buchnera and the facultative symbiont Arsenophonus.Compared to those of the control,symbiont bacterium abundance and composition of the treatment group were changed:the diversity of bacterial community was decreased,but the abundance of Buchnera was increased,while the abundance of Arsenophonus was decreased.Contrary to G0,G1 and G2 cotton aphid exhibited an increased relative abundance of Arsenophonus in sublethal treatment group.（2）Effects of deltamethrin stress on the symbiotic bacterial community of in three generations of A.gossypii.compared with the control group,the abundance and composition of the symbiotic bacteria were changed after the A.gossypii was exposed to deltamethrin:the diversity of bacterial community was decreased,and the abundance of Buchnera,Pseudomonadaceae and Burkholderiaceae were increased.In contrast to G0,the treatment group relative abundance of Pseudomonadaceae,Burkholderiaceae decreased in G1 and increased in G2.