THE USE OF ANTIBIOTICS TO ELIMINATE LATENT BACTERIAL-CONTAMINATION IN POTATO TISSUE-CULTURES

A simple leaf bioassay was developed to screen for slow-growing latent bacteria found in potato nodal cuttings. The potato cultures were established to provide a source of sterile leaf tissue for protoplast isolation and the bacteria were only detected after numerous generations in culture. In an attempt to solve this problem cultures were screened before and after various treatments. Two antibiotic mixtures were tested for their efficacy in eliminating bacteria: ABM1 contained penicillin, streptomycin, amphotericin and NaCl while ABM2 contained erythromycin, streptomycin and carbenicillin at various concentrations. Both cocktails, when added to the micropropagation medium, reduced plant growth, induced chlorosis at higher levels and did not eliminate contamination. In terms of protoplast isolation, the only effective treatment was when ABM1 was incorporated into the plasmolysis and enzyme media. It removed contamination at all levels tested and had a differential effect on cell division such that, at low levels of ABM1, protoplasts regenerated successfully.