Mechanism Of Astragalus Mongholicus Pesticide Residue In Response To Imidacloprid

Astragalus（Astragali Radix）is a Traditional Chinese Medicine（TCM）,Astragalus Mongholicus（Astragalus membranaceus（Fisch.）Bge.var.Mongholicus（Bge.）Hsiao）is the main source of Astragalus.In the process of large-scale planting,the pests and diseases leads to yield of medicinal materials decreased,and the abuse of pesticides may affect the quality of medicinal materials due to pesticide residues.At present,there are many studies on the standardized use and prevention and control effect of pesticides,but less attention is paid to the response of pesticide residues in plants and in soil.The work of this study is that:（1）2-year-old A.Mongholicus as the material,spray 1time,2 times,4times recommended concentration of imidacloprid.To observe aboveground biomass and root traits and analyze the effect of imidacloprid on the growth process of A.Mongholicus.（2）To determine the residual and degradation dynamics of imidacloprid in A.Mongholicus.plants and in soil.（3）To determine the effect of imidacloprid pesticide application on soil of A.Mongholicus environmental factors;（4）To determine the response process of A.Mongholicus to the physiological,transcriptional and metabolic levels of imidacloprid and summary analysis,try to reveal the mechanism of A.Mongholicus response to imidacloprid pesticide residues.The conclusion is as follows:（1）At 4 times the recommended concentration of imidacloprid pesticide,there were significant differences in the growth of leaf fresh weight,leaf dry weight,above ground fresh weight and ground dry weight,no significant differences between the other treatments and the controls.With the increase of imidacloprid,fresh weight,dry leaf weight,fresh weight on ground and dry weight of imidacloprid increased.At 4 times the recommended concentration of imidacloprid treatment,there is no significant differences in root length.However,there are significant differences with the root traits such as root diameter,root fresh weight and root dry weight.Other treatments were not significantly different from the controls,and root traits decreased with the total amount of imidacloprid used.The effect of imidacloprid pesticide on the aboveground biomass and root growth of A.Mongholicus began to appear after 20 d of application,and was eliminated at about 60 d.（2）A simplified Qu ECh ERS method of High Performance Liquid Chromatography tandem Mass Spectrometry（HPLC-MS/MS）was developed to determine imidacloprid pesticides in the leaves and flowers,roots and soil.The standard curve equation is well linearly in the range 0.5-20 ng?ml^-1,with a correlation coefficient R²>0.998.The LOD for imidacloprid detection was 1.0μg?kg^-1and the LOQ was 2.0μg?kg^-1,the RSD<5.7%,0.005-0.020 mg?kg^-1with average recovery of 90.83%.The digestion of imidacloprid pesticide with time was faster in leaves and flowers,with half-life of 0.53-1.22 d,0.49-1.02 d in roots,and longer half-life 15.93-25.58 d in soil.The digestion of the imidacloprid pesticide complied with the first-order kinetic equation,with R²>0.98.The residue of imidacloprid pesticide in the soil mainly exists in the topsoil layer above 20 cm.Pesticide residues in the root of A.Mongholicus are mainly absorbed by the aboveground parts such as leaves.（3）The OTU numbers of rhizosphere bacteria treated with imidacloprid were higher than those of the control group,and the highest number of OTU bacteria were treated at 2times the recommended concentration.The relative abundance of Acidobacteriota,Actinobacteriota,Bacteroidota,and Unclassified＿Bacteria at the phylum level varied significantly when treatment with different concentrations of imidacloprid.The relative abundance of MND 1,RB41,and Lysobacter varied significantly between treatments.The relative abundance of imidacloprid pesticide against A.Mongholicus rhizosphere fungi Unclassified＿fungi,Fusarium varied significantly between treatments.Imidacloprid significantly inhibited the activity of alkaline protease,cellulase,sucrase,β-glucosidase and urease in the cultivated soil of A.Mongholicus.Urease activity was inhibited at high doses of imidacloprid while nitrate reductase activity did not show differences in the test.The Ace,Chao 1,PD＿Whole-tree index of A.Mongholicus rhizosphere showed varied significantly between the imidacloprid treatments,which suggests that imidacloprid had an effect on bacterial community richness.The Simpson and Shannon index of fungi were significantly different between the treatments of imidacloprid,indicating that imidacloprid concentration affects the breadth of fungal distribution.Significant correlation was found between rhizosphere bacteria and fungi and soil physicochemical properties of A.Mongholicus.Therefore,it is inferred that the imidacloprid pesticide of A.Astragalus is transported to the root system through internal suction,thus affecting the microbial community structure in the rhizosphere.The change of soil enzymes and physicochemical properties are caused by pesticides directly settling in the soil,and their interaction changes the soil environment of A.Mongholicus.（4）Imidacloprid significantly affected the leaf physiology of A.Mongholicus.seedlings,the measured biochemical indicators show different dose effects,persistent effects and lag effects of imidacloprid.At the transcription level,some genes were significantly up-or downregulated,and the expression trend was obtained in 15 modules by differential gene expression trend analysis.Ribosomal pathway,galactose metabolism pathway,starch and sucrose metabolism pathway,fatty acid synthesis and decomposition processes were the main metabolic pathways enriched for differential genes.Imidacloprid had a significant effect on some of the leaves of A.Mongholicus.The results of the combined transcriptome and metabolome analysis of the up-up and down-down trend of differential genes and metabolites were mainly enriched in pantothenic acid and Co A biosynthesis,amino acid metabolism,amino acid metabolism and fat metabolism.The gene related to starch synthesis,GLGA,key enzyme gene for amino acid metabolism GAD,genes for fatty acid metabolism SAD,CYP 51,a key enzyme in lipid degradation gene,was all significantly up-regulated.In the process of imidacloprid stress,starch may accumulate in the chloroplast,protein degradation to maintain electrolyte balance,and fatty acid decomposition to increase free fatty acids in response to pesticide stress.In conclusion,the imidacloprid residues in A.Mongholicus changes the normal physiological and biochemical metabolic levels through the abiotic stress,imidacloprid concentration above 4RC affects the growth of A.Mongolicus.Imidacloprid pesticide changes the microbial community structure in the rhizosphere and affects the enzyme vitality and physicochemical properties of the 20 cm deep soil,but the two are indirect effects and jointly affect the growth environment of A.Mongolicus.The transcription and metabolic levels were enriched in A.Mongolicu leaves and starch and sucrose metabolism pathway,fatty acid synthesis and decomposition process,amino acid metabolism pathway,which response to pesticide residues in imidacloprid.