Effects Of Highly Efficient Degrading Microbe,Soybean And Imazethapyr On Soil Microbial Diversity

Imazethapyr is a broad-spectrum and highly effective herbicide,it is widely used in soybean fields,but imazethapyr remains in soil for a long time,it is easy to cause harm to the later crops,currently microbial degradation is one of the main governance method for removing its residues.In this paper,the degradation efficiency of imazethapyr degrading bacteria was evaluated by pot experiment,we analyzed the diversity of soil microbes by combining high-throughput sequencing with microbial plate culture,we discussed the relationship between soil microbial diversity and degrading bacteria,soybeans,and imazethapyr.The main results are as follows:The efficient degradation strains P2 and D1 were identified,and P2 was identified as Alcaligenes faecalis,and D1 was Serratia marcescens.We controll single variables of imazethapyr concentration,pH and temperature,setting up a gradient experiment,the most suitable degradation conditions for A.faecalis are:Imazethapyr is 100 mg/kg,the temperature is 30?,pH=7.The most suitable degradation conditions for S.marcescens are:imazethapyr is 100 mg/kg,the temperature is 25?,pH=8.Soil microorganisms were isolated by plate dilution method,we analyed the type and quantity of microorganisms in the soil,we texted the residues of pesticides in the soil by the high performance liquid chromatography,analying the residues of pesticides in the soil.The results showed:In the pot experiment that Trichoderma brevicompactum was as a degrading bacteria,after adding T.brevicompactum,it could inhibit other bacteria and fungi,by comparing with the control group,the number and species of soil fungi had changed significantly,and variety of bacteria was not obvious.After planting soybeans alone,the number and type of soil fungi did not change significantly,it had a promoting effect on the number of bacteria,and variety of bacteria was not obvious.The quantity and species of soil microorganism were significantly affected by the concentration of Imazethapyr.T.brevicompactum,soybean and imazethapyr three interaction between the experimental group and the control group had significant difference.As time goes on,the residues of imazethapyr in the soil gradually decreased,and the degradation efficiency was highest during 10 days to 20 days.T.brevicompactum,soybean and imazethapyr concentration all affected the degradation of imazethapyr.We analyzed the microbial diversity of soil samples and control group(original soil samples)on the 30th day through high-throughput sequencing technology.The results showed that T.brevicompactum,soybean,imazethapyr and their interactions had significant effects on soil microbial diversity.Soybeans have less effect on soil microbes than other groups.After the interaction between T.brevicompactum,soybean and imazethapyr,on the phylum level of the fungus,Ascomycota was significantly reduced,on the phylum level ofbacteria,Actinobacteria was significantly reduced,Proteobacteria was significantly increased.In the pot experiment which A.faecalis and S.marcescens were as degrading bacterias,S.marcescens and A.faecalis had no significant influence on the fungal diversity,and had significant effect on the diversity of bacteria,which could proliferate in the soil and inhibit the growth of other bacteria.Soybeans had a tendency to promote soil microbes,the number of fungi and bacteria were slightly higher than that of the control group,but there was no major change in the species.Imazethapyr had significant effect on microorganisms,if concentration of imazethapyr got higher and higher,the number of fungi and bacteria would become less and less,20 days later,the number of fungi gradually had returned to the control level,the types of fungi and bacteria were basically unaffected.When the two strains of highly degradable bacteria interacted with soybean and imazethapyr respectively,there were significant changes between test groups and control groups.Based on high-throughput sequencing technology,soil samples from the 20th day of treatment were analyzed,and soil microbial diversity before and after treatment was compared,the results showed that S.marcescens,A.faecalis,soybean and imazethapyr had significant effect on soil microbial diversity.Interaction of S.marcescens,soybean,imazethapyr and interaction of A.faecalis,soybean,imazethapyr have obvious effects on soil microbes.On the phylum level of the fungus,soybean,imazethapyr,A.faecalis(S.marcescens)and their interactions could reduce the abundance of Ascomycota,after adding A.faecalis,Zygomycota was significantly increased,on the phylum level ofbacteria,after the interaction between A.faecalis,Soybean and Imazethapyr,Bacteroidetes was significantly increased,after the interaction between A.faecalis,soybean and imazethapyr,Actinobacteria and Firmicutes were significantly reduced.This study provides theoretical and technical support for the microbial degradation of imazethapyr,we explore the diversity of soil microbes through the combination of traditional plate culture method and high-throughput sequencing technology,it has important theoretical significance for understanding the mechanism of the effect of remediation on soil microbes.