Screening,identification and characteristics of 2-methyl-4-chlorophenoxyacetic acid-degrading endophytic fungus from plants

【Objective】This experiment aimed to screen and identify 2-methyl-4-chlorophenoxyacetic acid(MCPA) -degrading endophytic fungi from plants and studied the degradation characteristics and pathway of the isolated endophytic fungi to MCPA. The study provided atheoretical basis for the bioremediation of herbicide-contaminated environment.【Method】Used plating method, endophytic fungus for degradation of MCPA were isolated from MCPA-contaminated Eupatorium odoratum. The isolated endophytic fungus was identified through morphological feature observed on the medium, combined with molecular biology method, cloning and sequencing of ITS, TUB and LUS sequences were conducted. The degradation conditions including temperature, pH, nutrition source were also optimized in the mineral salt medium by single-factor test. The degradation product of MPCA by endophytic fungi was identified in the mineral salt medium using high performance liquid chromatography(HPLC), gas chromatography-mass spectrometry(GC-MS) and liquid chromatography-mass spectrometry(LC-MS). In constant temperature incubator(30℃), endophytic fungi were added into nonsterile soil and sterile soil, and soil adding no endophytic fungi was as control group, and degradation rate of MCPA in soil were detected.【Result】An endophytic fungus strain(numbered E68), screened from E. odoratum, could effectively degrade MCPA.The E68 was identified as Xylaria arbuscula according to the analysis of its phenotypic feature and gene sequence. When the initial concentration of MCPA was 50.0 mg/L, the optimum degradation condition of MCPA was pH 5.0, temperature 28℃ and adding 0.5% glucose, the degradation rate was 97.03% after 7 d. The main production of strain E68 degrading MCPA was 4-chloro-2-methylphenol. Adding E68 into soil with 2.5 mg/kg MCPA could increase the degradation rate of MCPA in soil. Compared with soil without E68, the half-lives of MCPA increased 2.8 times in non-sterilized soil adding strain E68 and increased 2.5 times in sterilized soil adding strain E68.【Conclusion】The endophytic fungus E68 isolated from E. odoratum can effectively degrade MCPA in inorganic salt media and soils, and has potential value for the bioremediation of MCPA-contaminated environment.