The Screening Plant Endogenous Microbial And Degradation Characteristics Of The Study For 2-methyl-4-chlorophenoxy Acetic Acid By Fungal

The 2-methyl-4-chlorophenoxy acetic acid(MCPA),a herbicide of phenoxy acid herbicides,is a selective,transmitting absorption and hormone herbicide.MCPA is mainly used in small grains,rice,peas,and grass crops to control a variety of dicotyledonous broad weeds and some monocotyledon weeds.The widespread use of MCPA in sugarcane fields of Guangxi has raised increasing concerns about phytotoxicity problems on interplanting crops and later crops.Plant endophytes were screened from thatch,chromolaena odorata and guava and degradation characteristics of MCPA by endophytic fungi were studied in this experiment.These endophytes for biodegradation MCPA could provide a valuable source for the biodegradation of phenoxy acid herbicides.The results were summarized as follows:1.Isolation of MCPA degrading endophytic microorganismThe plate separation technology and enrichment culture was used to screen the bacteria and fungi from thatch,chromolaena,odorata and guava.The five strains,including tree strains bacteria and two strains fungi,were isolated and named as E47,E67,E69,E41,and E68,respectively.According to the experiment results,strains E41 and E68 were selected to study its degradation features.2.Identification of the degradation bacteria and fungiThe endophytes were identified through the morphological characteristics and molecular biology.The 16S rRNA gene sequences of E47,E67 and E69 were analyzed,and they were identified as Bacillus sp.,Curtobacterium sp.and Curtobacterium sp.,respectively.The ITS,TUB and LUS rDNA gene sequences of E41 and E68 were analyzed,and the morphological characteristics were observed under a light microscope,when fungus were incubated on PDB agar plate at 28.0 ? for 7 days.They were identified as Phomopsis sp.and Xylaria sp.,respectively.3.The degradation characteristics and dynamics of MCPADegradation rate of MCPA was detected by high performance liquid chromatography(HPLC).The influence factors including temperature,pH,and nutrition on the degradation of MCPA by this strain were optimized and degradation kinetics was analyzed by HPLC in this study.The results showed that degradation rate of MCPA by the strain E41 was 89.21%when the strain E41 was incubated in MM at 20.0-35.0 ?,pH=5.0-7.0 for 7 d with 50.0 mg/L of MCPA as the sole carbon source,and degradation rate of MCPA by the strain E68 was 95.93%when the strain E68 was incubated in MM at 20.0-30.0 ?,pH=4.0-5.0 for 7 d with 50.0 mg/L of MCPA adding 0.5%glucose.The degradation dynamics research indicated that half-life of MCPA was 1.7 d at presence of the strain E41 at 28.0 ?,pH=7.0 with 50.0 mg/L,and half-life was 3.0 d at presence of the strain E68 at 28.0 ?,pH=5.0 with 50.0 mg/L.4.The degradation products of MCPADegradation products of MCPA by E41 and E68 were identified as 4-Chloro-2-methylphenol using gas chromatography-mass spectrometry(GC-MS)and liquid chromatography-mass spectrum(LC-MS/MS).The content of 4-chloro-2-methylphenol was 12.18 mg/L and 1.41 mg/L for 7 d,when MCPA was degraded in MM by E41 and E68.4-Chloro-2-methylphenol has a downward trend.5.Application of degrading fungiSoil remediation experiment was simulated in the indoor.The results showed that half-life of MCPA were 12.84,2.07 and 4.62 d in non-sterilized,non-sterilized +E41 and non-sterilized +E68 three treatments,respectively.The results showed that half-life of MCPA were 27.73,2.73 and 11.00 d in sterilized,sterilized +E41 and sterilized +E68 three treatments,respectively.The results suggested that strain E41 and E68 may increase the speed of MCPA degradation in soil and sterilization soil.The pot experiment showed that cabbage growths were better in soil inoculated E41 or E68 than not inoculated.The hydroponic experiments demonstrated that rice growth were better in degradation liquid.