Optimizing Suitable Antibiotics for Bacterium Control in Micropropagation of Cherry Rootstock Using a Modified Leaf Disk Diffusion Method and E Test
2019
Chenglin Liang | Rendun Wu | Yu Han | Tian Wan | Yuliang Cai
Bacterial contamination is a major and constant threat to the establishment and subculture of in vitro plant culture. In this study, we used a slightly modified qualitative disk diffusion method to screen optimal antibiotics to control the growth of bacterial contaminants isolated from explants of cherry rootstock &lsquo:Gisela 6&rsquo:. Bacterial susceptibility to eight different antibiotics was tested. The results showed that tetracycline was the most effective antibiotic for controlling bacterial growth: cefotaxime, carbenicillin, kanamycin, and streptomycin were less effective, whereas ampicillin, penicillin, and cefazolin did not inhibit growth of the isolated bacteria. Using the quantitative E test, the minimal inhibitory concentration (MIC) of tetracycline was determined to be 1.0 µ:g mL&minus:1. We also measured the Fv/Fm values, chlorophyll content, and enzymatic activity of superoxide dismutase and peroxidase to explore the effect of different tetracycline concentrations, 0, 0.064, 0.5, 1.0, 16, and 256 µ:g mL&minus:1, on the growth of bacteria and explants over 30 days. Results indicated that 1.0 µ:g mL&minus:1 tetracycline was effective in restricting bacterial growth, with non-significant negative effects on explants at low concentrations, but were enhanced negative effects at high concentrations. The application of the disk diffusion method and E test enabled the identification of an antibiotic and its MIC value effective for eliminating bacterial contaminants while causing minimal damage to explants, indicating a high potential of these methods to control bacterial contaminants in in vitro plant culture.
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