AN EVALUATION OF ANTIBIOTICS FOR THE ELIMINATION OF XANTHOMONAS-CAMPESTRIS PV PELARGONII (BROWN) FROM PELARGONIUM X DOMESTICUM CV GRAND SLAM EXPLANTS IN-VITRO

A range of antibiotics was evaluated for activity against Xanthomonas campestris pv. pelargonii (Xcp) on diagnostic sensitivity testing and plant tissue culture media. Many of the antibiotics showed reduced or no activity on the latter. Tetracycline and cefotaxime, chosen for further investigation, were screened for light stability under plant culture regimes. Tetracycline was inactivated in photosynthetic photon fluxes of 22 mumol m-2 s-1 and above. The minimum bacteriocidal concentration of cefotaxime was determined in bacteriological and plant tissue culture media. Cefotaxime was further tested for phytoxicity and ability to eliminate Xcp from deliberately infected explants. Cefotaxime was shown to eliminate contamination and stimulate the growth of the plant tissue cultures up 500 mg l-1.