Isolation And Identification Of Plant Endophytes Capable Of Degrading Chlorpyrifos

Chlorpyrifos is an alternative to highly toxic organophosphorus pesticides which used largely and extensively in Chinese agriculture, as a result brings huge hidden danger to agricultural product. Endophytes are nonpathogenic microorganisms that colonize living plant tissue for lifetime or at least a certain stage of life. Compare with microbe isolated from soil, endophytes can effectively colonize in plant and suffer less environmental influences. Based on this, it’s expected to become a new way to control the risk of residue contamination caused by utilization of pesticide largely, which employe the plant endophytes capable of degrading pesticide to accelerate the metabolism and degradation of pesticide residue in plant.We applied the surface sterilization and grinding method, to successive screen and isolate the endophytes capable of degrading chlorpyrifos from the plant horseweed herb(Conyza canadensis(L.)Cronq) collected near the waste pool of a pesticide plant, Chinese chives(Allium tuberosum Rottl. ex Spreng) and rice(Oryza saliva subsp, keng) by using Minimal salts media(MSM) modified with chlorpyrifos as the sole carbon. We also investigated the degrading characteristics of the isolates inside and outside plant, identified the endophytes through physiological-biochemical test combined with 16 Sr DNA sequence analysis. For further exploration on the management of degradation mechanism of residual chlopyrifos and other pollution in plant through endophytes, and the result of this work can provide theoretical direction for utilizing endophytes to regulate pesticide residue in agriculture products, an new vision to control and manage agricultural residue pollution. The main results are as follow:1、A Cronobacter sp. strain XFP-gy was isolated from horseweed herb. It could degrade 77.28% of chlorpyrifos(20 mg/L) after 9 days inoculation. The growth of strain XFP-gy could be promoted and degradation rate could be enhanced up from 69.59% to 98.0% at 5th day by adding additional carbon source in MSM. The optimal condition for XFP-gy degrading chlorpyrifos is 30℃, and p H is 7.0. Under this optimal incubation condition, the chlorpyrifos degradation efficiency by strain XFP-gy increased with the increasing original bacterium inoculum density, and decreasing initial chlorpyrifos concentration in the media.2、A Sphingomonas sp. strain HJY was isolated from Chinese chives. It could metabolized 95.88% of 20 mg/L chlorpyrifos within 15 days in MSM; And additional 1% glucose could increase the degradation rate to 98.48% within 6 days; The optimal condition for maximum removal of chlorpyrifos was found to be: chlorpyrifps initial concentration of 10 mg/L, inoculums density of 2%, p H 6 and temperature of 30-35℃.3、5 endophytic bacterium capable of degrading chlorpyrifos were isolated from japonica rice,they were strain DG(Pseudomonas aeruginosa), strain DGB(Bacillus megaterium), strain DJ(Sphingobacterium Canadense),strain DJA(Pseudomonas)and strain DJB(Pseudomonas).These endophytes not only possess the ability to degrade chlorpyrifos outside the rice, but also boost rice growth through indoleacetic acid(IAA) secretion, Phosphate solubilisation, 1-aminocyclopropane-1-carboxylate(ACC) deaminase and Siderophore production, furthermore accelerate the chlorpyrifos decreasing in rice, soil at the root and the paddy by inoculating these endophytes into the rice.