Research On Quinclorac Degrading Bacteria Screening, Identification And Application

Quinclorac as hormone herbicide, has been widely used in paddy barnyardgrass prevention process, but its half-life in the rice fields is long and accumulated year by year. Quinclorac residued in the soil makes the tobacco leaves bubble deformity, in severe cases, causes the blades elongated strip. Thus the blades will lose value and tobacco production will be affected severely. To solve Quinclorac residual contamination problem, we have screened quinclorac degrading bacteria and studied its characteristics. The main contents are as follows:(1) We sampled from perennial application quinclorac paddy soil, domesticated the soil samples. Then we initially received 12 degrading bacteria strains by By enrichment culture and selection training. We inoculated the 12 degrading bacteria strains into quinclorac salts medium and cultured at 28℃, 150 rpm shaker for 7 days. Detected content of residual quinclorac and calculated the degradation rate. Degradation rate of degrading bacteria MC-10 reaches 90%, as the object of further study.(2) We observe colony morphology of MC-10 and cell morphology with an electron microscope, then studied physiological and biochemical characteristics of MC-10. Extracted DNA of degrading bacteria MC-10, determined its 16 S r DNA sequences, builded phylogenetic tree, finalized recognized degrading bacteria MC-10 as Arthrobacter sp.(3) Best degradation conditions of degrading bacteria MC-10 is 30℃, p H=7. When inoculum is 5%, MC-10 can degrade quinclorac efficiently range 1 mg/kg to 100 mg/kg.(4) We surveyed the number of MC-10 colonies in soil by dilution plate method, finded that the number of colonies gradually decreased over time. After 50 days of culture, the number of colonies stable over 106cfu/g, which show degrading bacteria MC-10 can colonize the soil well.(5) Inoculated degrading bacteria MC-10 into 10mg/kg quinclorac toxic soil. After cultured in the incubator at 30℃ 7 days, the content of residual quinclorac is 1.76 mg/kg and the degradation rate reaches 70%.(6) In order to understand the mitigation effection to quinclorac injury, we launch pot experiment in a climatic chamber. The results showed that, the experimental treatment which inoculated degrading bacteria MC-10 before transplanting 30 days can alleviate Quinclorac injury effectively. The experimental treatment which inoculated degrading bacteria MC-10 after transplanting can alleviate injury to some extent, injury response rate reaches 40% after transplanting 60 days. So we should inoculate degrading bacteria MC-10 before transplanting tobacco in order to minimize quincloracinjury.