Screening And Degradation Characteristics Study Of Nicosulfuron And Imazamox Degrading Bacteria

Sulfonylurea herbicides and imidazolinone herbicides are the two most applied pesticides in China.It has the advantages of high activity,low dosage,broad herbicidal spectrum,and strong selectivity.Used to control field weeds in crops such as beans,peanuts and corn.Nicosulfuron in sulfonylureas and imazamox in imidazolinones are widely used in farmland in northern China.Since these two herbicides are long-lasting herbicides,long-term use will affect the later crops.It has caused people's concern and caused pollution to the soil and its surroundings.This article focuses on the screening of dominant strains of nicosulfuron and imazamox,as well as their degradation characteristics and soil remediation.It is expected to provide scientific information for the rational use and environmental safety evaluation of sulfonylurea and imidazolinone herbicides.The main research contents and methods of this experiment:The enriched culture technique was used to screen the mixed flora that could degrade the herbicide,and the selected mixed flora was separated and purified by plate streaking for several times.Test the ability of a single strain to degrade herbicides,determine the extraction method and detection method of pesticides,and verify the recovery rateThe effects of environmental influence factors on the degradation efficiency of dominant bacteria were studied from three aspects: temperature,pH and inoculation amount,and the digestion kinetics of the strains were studied.Response surface methodology was used to optimize the degradation conditions.Under the optimal conditions,the effect of the initial herbicide concentration in the range of 10mg/L-400mg/L on the degrading bacteria was investigated,and the relationship between the growth curve of dominant bacteria and the degradation ability,as well as suitable microbial degradable herbicide concentration was analyzed.Finally,pot experiments were used to verify the soil remediation ability of the dominant bacteria.1.A total of 1 strain of nicosulfuron-degrading bacteria HX06 and 2 strains of imazamox-degrading bacteria JX02 and JX06 were screened by enrichment culture technology.The strain HX06 was identified as Aspergillus fumigatus,and the strains JX02 and JX06 were identified as Streptomycetaceae.The half-life of degradation of 150mg/L nicosulfuron by strain HX06 was 3.32 d,and the half-life of degradation of 150mg/L imazamox by strains JX02 and JX06 were 1.46 d and 1.27 d respectively.2.After optimizing the degradation characteristics of three degrading bacteria,it was found that the degradation rate of 100 mg/L nicosulfuron in MEA medium within 7 days of HX06 strain was 79.3%;Strain JX02 can degrade imazamox in the initial concentration range of 50-400mg/L in LB medium for more than 95% in 3.5 days;JX06 strain could completely degrade imazamox in concentrations of 50-100mg/L in LB medium within 3.5 days.3.In the pot experiment,the three strains of degrading bacteria all had significant effects on the repair of herbicides in the soil,and the degradation ability of the three strains was not affected by soil microorganisms.Soil microorganisms can significantly promote the degradation ability of strain JX06.In the experiments of degradation in different concentration ranges,Strains HX06 and JX06 have poor degradation ability on high-concentration herbicides.It can be clearly seen in the bioremediation experiment that the growth of plants in the soil treated with degrading bacteria is better than that of the plants without added strains.It can be explained that the three strains of degrading bacteria effectively deal with the environmental problems caused by herbicides,and provide a basis for future research and development of bacteria.