A RISK ASSESSMENT STUDY OF PLANT GENETIC-TRANSFORMATION USING AGROBACTERIUM AND IMPLICATIONS FOR ANALYSIS OF TRANSGENIC PLANTS

Agrobacterium transformation systems for Brassica, Solanum and Rubus, using carbenicillin, cefotaxime and ticaracillin respectively to elimi nate contamination, were examined for the presence of residual Agrobac terium. The results indicated that none of the antibiotics in question , succeeded in eliminating Agrobacterium and the contamination levels increased in explants from 12 to 16 weeks to such an extent that Solan um cultures senesced and died. This may be due to the fact that four t imes the Minimum bactericidal concentration values (concentration to b e used for elimination of contaminants in culture), for the three anti biotics, were higher than the concentrations employed in the culture m edium. Contamination in shoot material decreased over 16 to 24 weeks p ossibly due to bacteriostatis and the use only of the apical node for further culture. The presence of the binary vector was also noted unde r non-selective conditions, even up to 6 months after transformation, where approx. 50% of contaminated material still harboured bacterial c ells with the binary vector at levels of approx. 10(7) Colony forming units per gram.