FIELD PERFORMANCE OF TRANSGENIC POTATOES

Field performance was assessed in 13 transgenic potato (Solanum tuberosum L.) lines from three cultivars expressing a selectable marker gene conferring kanamycin resistance. All lines developed unexpected changes in the phenotypic appearance of shoots, and/or poor tuber yield generally involving a reduced number of small tubers. Each independently selected transgenic line showed distinctly different changes in phenotypic appearance or yield performance. The observed changes were very uniform within each clonally propagated transgenic line, and were consistent in appearance over two seasons in the field. These changes were attributed to either epigenetic or genetic events occurring during the tissue culture phase of transformation. Efficient systems for the rapid selection and regeneration of transformed plant cells are therefore required to minimise the frequency of tissue culture induced variation in plant performance.