Screening Of Strains For Degrading Flurochloridone And Their Degradation Effects

The flurochloridone,a new selective herbicide with high selectivity,was widely used in the world.It can effectively control various broad-leaf weeds and annual grasses in crops such as winter wheat,sunflower,cotton and potato.However,flurochloridone was limited by the promotion because of the long half-life and slow degradation rate under natural conditions.The microbial degradation was one of the effective means to reduce the pollution of the herbicide.In this study,strains FL-M-2,FL-M-3 and FL-G-2 that can stably and efficiently degrade flurochloridone were obtained by soil enrichment from potato field.These three strains provided the germplasm resources for the practical application of microbial degradation of flurochloridone.The strains obtained by screening with a degrading effect were used as research materials,and the most optimal conditions of degradation of each strain were studied by single factor experiments;the safety of each strain on crops was evaluated by seed germination experiments;the degradation effect of flurotrione of these strains in soil was studied by by pot simulation experiments.The results are described as follows:(1)The strains were screened by enrichment method and plate dilution method,and the degradation rate of flurochloridone by each strain was detected and analyzed by liquid chromatography-tandem mass spectrometry(LC-MS/MS).Three strains degrading flurochloridone were isolated and screened from potato field soil.Through morphological observation and molecular identification of the three strains,it was identified that the strain FL-M-2 was Purpureocillium lavendulum,the strain FL-M-3was Didymellaceae sp.,and the strain FL-G-2 was Streptomyces parvus.When the inoculum was 5%,28 ℃,180 r/min shaking culture for 14 days,the degradation rates of 1 mg/L flurochloridone were 50.82%,73.43% and 84.37%,respectively.(2)The degradation characteristic of the three strains was investigated by single factor experiments.When the inoculation was 5%,the degradation rates of strains FL-M-2,FL-M-3 and FL-G-2 all reached the maximum.After 6 days of culture,the three strains degraded flurochloridone with a degradation rate of 39%,73% and 65%,respectively.When the p H value was 6,the effect of the three degrading strains reached the best.The highest degradation rates were observed after 6 days of culture,which were 41%,74% and 68%,respectively.When the culture temperature reached30°C,and the highest degradation rate was observed after 6 days of culture,which were 42%,75% and 70%,respectively.The degradation rates of strains FL-M-2,FL-M-3 and FL-G-2 gradually increased with the increasing of culture time,and the degradation rates of flurochloridone were 57.92%,75.72% and 96.80%,respectively.The degradation rate of FL-G-2 of fermentation was 87.30% higher than that of the blank control at 49 days of culture.The inhibitory effect of flulofenone on the three degrading strains increased with the increasing of substrate concentration.The strains had a good effect on the degradation of low concentration substrates,and had a high tolerance to flurochloridone concentration.When the concentration of flurochloridone was 10 mg/L,all strains could grow.(3)Using wheat and rapeseed as receptors,the safety of flurochloridone-degrading strains on crops was studied by seed germination method.When the strain concentration was 1×108 cfu/m L,the germination rates of rape and wheat treated with clear water were not significantly different from other treatments;the root length and dry weight of rape treated with the three degrading strains were not significantly different from those of the control.No significant difference between the rapeseed shoot length and fresh weight treated with strains FL-M-3 and FL-G-2and the clean water control group;the root length,shoot length and dry weight of the wheat treated with the three degrading strains were compared with the control group.There was no significant difference between the groups.The results showed that the three degrading strains had no obvious inhibitory effect on the growth of wheat and rape.The soil remediation experiments of flurochloridone showed that the removal efficiency of flurochloridone was significantly improved after the flurochloridone degrading strains FL-M-2,FL-M-3 and FL-G-2 were added to the soil.FL-G-2 had the highest degradation rate.After 7 days and 14 days,the degradation rates of flurochloridone treated with T4 were 60% and 77.3%,respectively,which were 52%and 62.6% higher than that of the blank control group,respectively.The results of seedling emergence rate,root length,shoot height and fresh weight and dry weight of wheat and rapeseed under different treatments showed that the root length,fresh weight and dry weight of rapeseed in T1 treatment were inhibited compared with CK treatment,while the three degrading strains had lower root length,fresh weight and dry weight.All additions weakened the inhibitory effect of flurochloridone on rape growth indexes,and the repair effect of T4 treatment was the best.Compared with the control soil,the emergence rate,seedling height,root length,fresh weight and dry weight of wheat were all inhibited in the treatment with flurotrizone pollution.The weakening effect was not significant;however,the root length,fresh weight and dry weight of wheat treated with degrading strains T3 and T4 were significantly higher than those of T1,and the emergence rate of wheat treated with T4 had no significant difference compared with CK.