Target Cells for Gene Transformation - The first step in gene transfer technology is to select cells that are capable of giving rise to whole transformed plants. Transformation without regeneration and regeneration without transformation are of limited value. In many species, identification of these cell types is difficult.

 This is unlike the situation in animals, because the plant cells are totipotent and can be stimulated to regenerate into whole plants in vitro via organogenesis or embryogenesis. However, in vitro plant regeneration imposes a degree of 'genome stress', especially if plants are regenerated via a callus phase. This may lead to chromosomal or genetic abnormalities in regenerated plants a phenomenon referred to as soma clonal variation.