The cell biology of plant transformation: Current state,problems, prospects and the implications for the plant breeding

Summary The DNA delivery systems which are routinely used to introduce genes into crop plants are Agrobacterium tumefaciens, electroporation and particle bombardment. The differences and similarities between these different transformation techniques are outlined. The influence of the cell biological approach, and more specifically the impact of the state of the plant cell at the moment of transformation, on the genotype and phenotype of the regenerated transgenic plant is analysed. In this respect phenomena such as position effects, gene silencing, co-suppression, epistasis, co-transformation and somaclonal variation are discussed. The relevance of these factors for plant breeders is discussed.