Expression and inheritance of kanamycin resistance in a large number of transgenic petunias generated by Agrobacterium-mediated transformation.

One hundred and four kanamycin-resistant Petunia "Mitchell" plants were regenerated from leaf discs cocultivated with Agrobacterium tumefaciens strain LBA4404 containing a binary vector pCGN200. Selection for kanamycin resistance was applied during plant regeneration at the initiation of both shoots and roots. The regenerated plants were analysed for expression and inheritance of their kanamycin resistance phenotype. Approximately half of the plants showed normal Mendelian inheritance for one or two kanamycin resistance genes. In one case, the two copies were inserted at closely linked sites on homologous chromosomes, and gave <0.05% kanamycin-sensitive progeny on backcrosses. Six plants had inheritance patterns suggesting that the kanamycin gene had inserted into an essential region of DNA. Forty-five plants showed lower than expected transmission of kanamycin resistance, which was associated with low expression of the resistance phenotype in most cases. Ten plants produced segregation ratios that are not readily interpreted by Mendelian inheritance.