Effects of antibiotics on in vitro-cultured cotyledons

Here, we report the effects of kanamycin (Km), cefotaxime (Cef), carbenicillin (Crb), and ampicillin (Amp) on morphogenesis of Chinese cabbage (Brassica rapa L. ssp. pekinensis) cultured on Murashige and Skoog medium. The four antibiotics had little effect on callus induction, but influenced shoot and root differentiation to different degrees. Even very low concentrations of Km inhibited redifferentiation of buds and roots from callus. We also found that Cef inhibited redifferentiation at a relatively low concentration and delayed organ morphogenesis. Crb had no obvious effect on bud, shoot, or root differentiation, whereas Amp stimulated root and shoot differentiation within the range 0–1,000 mg/L. The higher concentrations of Amp promoted greater stimulation of shoot differentiation. At 1,000 mg/L Amp, the shoot differentiation frequency reached 93.3% compared to 73.6% for control treatments without antibiotic supplementation. Thus, Km can be used as a selective agent for transgenic plant tissues that carry appropriate selection markers, whereas Amp (at a high concentration) or Crb may be beneficial for use in tissue culture and genetic transformation of Chinese cabbage.