Transformation of diploid potato genotypes through Agrobacterium vectors and expression of T-DNA markers in root clones, regenerated plants and suspension cells

Stem internodes of three diploid potato genotypes (lines HH260, C and E) were transformed with binary Agrobacterium strains, containing the A. rhizogenes wild type plasmid pRil855 together with the plasmid construct pBI 121, to introduce a set of selectable and reporter marker genes (coding for hairy root phenotype, hormone autotrophy, opine synthesis, kanamycin resistance and P-glucuronidase activity). Genetic marker lines were produced at the level of root clone, plant (regenerated from root clone segments) and cell suspension culture (established from callus induced on leaf segments). Transformation frequencies and the expression of transformation marker characters were dependent on the genotype, the physiological state of the internodal explants and the Agrobacterium strain. Root clones, derived from stem internodes producing transformed roots in high numbers, generally showed a complete set of marker characters and prolific growth, in contrast to the root clones that originated from less productive stem internodes. Shoot regeneration was achieved from the genotypes HH260 and C, but not from genotype E. Loss of one or more marker characters (opine synthesis, kanamycin resistance, GUS activity) was observed in half of the regenerants, as compared to their original root clones. Cell suspension cultures showed expression of all marker characters present in the original transformed plant. The majority of the transformed marker lines, at the level of root clone, regenerated plant, or cell suspension culture, had maintained the original diploid level.