Study On Ecotoxicity Of Thifluzamide To Earthworms And Its Effect On Soil Fungal Community

Thifluzamide is a typical succinate dehydrogenase inhibitor fungicide,which has a high control effect on diseases caused by basidiomycetes.Preliminary research found that thifluzamide used as a seed treatment to control maize sheath blight has a high control effect and was very safe for corn within a certain dose range,but its release into the soil as a seed treatment will inevitably bring soil Residues and their impact on the soil ecological environment.At present,the effect of thifluzamide on soil ecology is poorly understood.Therefore,this study used simulating lab test to comprehensively evaluate the effect of thifluzamide on the soil model organism Eisenia fetida from the perspectives of individual,biochemical and molecular levels;The effects of thifluzamide on soil respiration and the number of cultivable fungi were studied through traditional methods of research in soil science,and the effects of exposure to thifluzamide on the abundance and diversity of soil fungi were discussed in combination with high-throughput sequencing.Finally,the effect of thifluzamide on soil fungal function was analyzed by using FUN Guild function prediction.The results of this study provide a theoretical basis for the environmental safety assessment of thfluzamide and provide technical support for the registration of thiafluzamide as seed coating formulations.The main results were as follows:(1)Individual level studies have found that high-concentration thifluzamide treatment(10.0 mg/kg)inhibited the weight gain of earthworms and reduced the number of earthworm cocoons and juvenile earthworms.However,treatment with low concentration of thifluzamide(0.1 mg/kg and 1.0 mg/kg)had no significant effect on the phenotype of earthworms.(2)At the biochemical and molecular levels,thifluzamide treatments significantly inhibited the activities of earthworm target enzyme SDH and respiratory chain complex Ⅱ,and induced related subunit genes on the respiratory chain complex(NADH1,SDHB,Cox Ⅰ,Cox Ⅱ)up-regulated expression and down-regulated expression of ATP6 gene;Thifluzamide leads to an increase in ROS levels in earthworms,and an increase in MDA content at 7 days of sampling;Thifluzamide induced abnormal changes in the activities of antioxidant enzymes(SOD,CAT and POD)and detoxification enzymes(GST)in the body,and the metallothionein gene(MT)gene related to antioxidant defense was significantly down-regulated at the 7th day of sampling,and the expression was up-regulated to varying degrees during the subsequent 14,21,and 28 days sampling;Earthworm DNA was damaged at the lowest dose(0.1mg/kg)of thifluzamide treatment,and the degree of damage(OTM)increased with the increase of thifluzamide concentration,showing a very significant dose-response relationship.(3)In this study,maize field soils were collected from Tai ’an,Shandong Province and Guoyang,Anhui Province,and identified as sandy loam and cinnamon soil,respectively,and cultured in laboratory.The effect of thifluzamide on soil basal respiration was measured by static chamber method,and the study found that thifluzamide exposure promoted soil basal respiration;The effect of thifluzamide on the number of cultivable fungi in two soils was measured by the dilution coating plate method,and it was found that thifluzamide can significantly reduce the number of cultivable fungi in soils after exposure.(4)In the middle and late stages of the trial on both soils,thifluzamide exposure reduced microbial diversity in two soils;Altering the relative abundance of some fungal communities,and can change the community structure of fungal microorganisms.Among them,the fungal diversity and community structure are closely related to the sampling time and the treatment dose of thifluzamide.(5)The FUN Guild function prediction after exposure to different concentrations of thifluzamide shows that the soil fungi in the two places are mainly saprotroph;In Tai ’an soil,the relative abundance of Undefind Saprotroph fungi increased after treatment with thifluzamide,especially in high concentrations(10 mg/kg),while the relative abundance of pathologic fungi(plant pathogens)decreased in samples taken 30 and 60 days after treatment with 1.0 mg/kg and 10 mg/kg thifluzamide;Similarly,the relative abundance of Undefind Saprotroph increased and the relative abundance of plant pathogens decreased in Guoyang soil after treatment with thifluzamide.