Research Of The Sublethal Effect Of Nitenpyram On Nilaparvata Lugens Under Elevated CO₂ Concentration

In this study,we used Nilaparvata lugens St（?）l,a major rice pest,as the test insect,and set two CO₂concentrations（ambient CO₂and elevated CO₂concentrations）.Also,the sublethal concentration LC₃₀of nitenpyram were treated with N.lugens.The two-sex life table was used to analyze the effects of different CO₂concentrations on the life history parameters and population dynamics of N.Lugens.And we studied the effect of sublethal nitenpyram on the physiological metabolism of the mother and offspring of brown planthopper under elevated CO₂,analyzed the differences in the relative expression levels of stress resistance genes and detoxification enzyme genes.Meanwhile,we conducted continuous 10 generations of resistance breeding for N.lugens under different CO₂concentrations,and evaluated the risk of resistance to nitenpyram under elevated CO₂.The research of this paper aims to explore the biological response and resistance risk of N.lugens after the application of nitenpyram under elevated CO₂.The results are as follows:1.Effects of sublethal nitenpyram on the life history parameters and population dynamics of N.Lugens under elevated CO₂Using the two-sex life table,analyzed the effects of sublethal nitenpyram under different CO₂concentrations on the life history parameters and population dynamics of the mother（F₀）and offspring（F₁）of N.lugens.The results showed that the development duration of the mother generation（F₀）of N.lugens under elevated CO₂was significantly shorter than that under the ambient CO₂treatment（P<0.05）.Higher intrinsic growth rate（r）、finite rate（λ）and net reproduction rate（R₀）were observed in elevated CO₂than those in ambient CO₂treatment,but did not reach a significant level（P>0.05）.Under elevated CO₂,the development duration of N.lugens offspring（F₁）was lower than those in ambient CO₂treatment,but did not reach a significant level（P>0.05）.However,significantly higher adult fecundity was found in elevated CO₂than those in ambient CO₂treatment（P<0.05）.The adult lifespan was higher in elevated CO₂than ambient CO₂treatment,but the difference was not significant（P>0.05）.Also,the Intrinsic growth rate（r）、finite rate（λ）and net reproduction rate（R₀）were higher in elevated CO₂treatment than those in ambient CO₂concentration,there were no significant difference（P>0.05）.The results showed that elevated CO₂concentration could promote the nymphs development,adult reproduction and population parameters of N.lugens treated with sublethal concentration of nitenpyram.2.Effects of sublethal concentration of nitenpyram on the physiological metabolic enzyme activities of N.lugens under elevated CO₂After treated with sublethal concentration of nitenpyram,there were no significant difference in the total protein content（TP）,amino acid content（AA）,esterase（EST）and glutathione S-transferase（GST）activities of N.lugens under elevated CO₂concentration and ambient CO₂treatments（P>0.05）.However,significantly higher catalase（CAT）and superoxide dismutase（SOD）and lower cytochrome P450 multifunctional oxidase（P450）were observed in elevated CO₂than those in ambient CO₂（P<0.05）.Also,there were no significant difference in TP,AA,and EST in the progeny generation of N.lugens under elevated CO₂and ambient CO₂treatments after treated with sublethal nitenpyram（P>0.05）.While,significantly lower the activities of CAT and SOD and higher P450 and GST were found in elevated CO₂than those in ambient CO₂（P<0.05）.The results showed that the activities of protective enzymes of N.lugens were inhibited under elevated CO₂after treating with sublethal concentration of nitenpyram,and the detoxification enzyme activities of P450 and GST in the progeny generation of N.lugens increased to enhance the detoxification metabolism of nitenpyram.3.Effect of sublethal concentration of nitenpyram on relative expression levels of related genes of N.lugens under elevated CO₂After treated with sublethal concentration of nitenpyram,the relative expression levels of Nl HSP68,Nl Vg,Nl Car E19 and Nl CYPER1 genes of N.lugens were significantly up-regulated under elevated CO₂compared with ambient CO₂treatment（P<0.05）.While,there were no significant differences in the relative expression levels of Nl HSP90,Nl Car E1,and Nl CYPAY1 genes between elevated CO₂and ambient CO₂treatments（P>0.05）.Also,there were no significant difference in the relative expression levels of Nl HSP68,Nl HSP90,Nl Vg,Nl Car E1,Nl Car E19,Nl CYP6ER1 and Nl CYP6AY1genes in the progeny generation of N.lugens under elevated CO₂compared with ambient CO₂treatment after treating with sublethal concentration of nitenpyram（P>0.05）.The results showed that after treated with sublethal concentration of nitenpyram,N.lugens could increase the expression of Nl Vg to stimulate reproduction under elevated CO₂,leading to a higher likelihood of resurgence compared with ambient CO₂concentration.4.Risk assessment of resistance of N.lugens to nitenpyram elevated CO₂The brown planthopper screened continuously for 10 generations with nitenpyram under ambient CO₂and elevated CO₂concentrations.The LC₅₀of N.lugens increased from 1.6557 mg/L to 5.2431 mg/L under ambient CO₂concentration,and the resistance ratio reached 3.08-folds.The realistic heritability of resistance calculated by threshold trait analysis was 0.1202.When the average mortality rate of each generation was 50%,it would take 21 generations for the resistance to increase to 10-folds.The LC₅₀of N.lugens increased from 3.3855 mg/L to 5.0601 mg/L under elevated CO₂concentration,and the resistance ratio reached 1.49-folds.The realistic heritability of resistance calculated by threshold trait analysis was 0.0493.When the average mortality rate of each generation was 50%,it would take 51generations for the resistance to increase to 10-folds.The resistance risk of brown planthopper to nitenpyram under elevated CO₂was lower than those in ambient CO₂concentration.In summary,elevated CO₂can promote the individual development,reproduction,and population parameters of N.lugens.After treated with sublethal nitenpyram,the protective enzymes activities of N.lugens were inhibited,and the activities of P450 and GST increased under elevated CO₂.The relative expression levels of Nl HSP68,Nl Vg,Nl Car E19,Nl Car E19 and Nl CYP6ER1 genes of N.lugens were significantly up-regulated in elevated CO₂compared to ambient CO₂concentration.It was found that the resistance risk of N.lugens to nitenpyram under elevated CO₂was lower than in ambient CO₂screened continuously for 10 generations with nitenpyram.The research results of this study can provide data support for the integrated control of N.lugens under global warming caused by increasing atmospheric CO₂concentration in the future.