An antibiotic-based selection strategy to regenerate transformed plants from apricot leaves with high efficiency

Different selection strategies were developed to regenerate transformed plants from leaves of the apricot cultivar Helena (Prunus armeniaca). A delay in the application of inhibitory-to-regeneration concentrations of the antibiotic paromomycin was necessary in order to get transformed plants. The antibiotic concentration was gradually increased in the regeneration medium to improve elimination of escapes. Transformed GFP-expressing buds were recovered and increasing concentrations of the antibiotic were applied to eliminate possible remaining escapes and chimerical plants. Transformation efficiencies ranged from 3.5 to 5.8%, although they were not significantly different between strategies. However, large significant differences were found in the number of escapes that each selection strategy produced. Significantly higher rooting percentages of transformed than of control shoots were obtained at 40 μM paromomycin. Southern blot analysis of several randomly chosen PCR-positive lines confirmed the integration of the nptII transgene. This work constitutes one of the few on transformation of a cultivar from Prunus species.