Marker-free transformation: increasing transformation frequency by the use of regeneration-promoting genes

The generation of transgenic plants free of antibiotic resistance markers is a major challenge to plant biologists and plant breeders. Currently, there are two main strategies to achieve this goal: one approach is to excize or segregate marker genes from the host genome after regeneration of transgenic plants, and the second is based on so-called ‘marker-free’ transformation. Marker-free transformation has been successfully demonstrated by the use of several plant and non-plant genes that are capable of promoting explant regeneration. This approach appears not only to be effective for the generation of marker-free transgenic plants, but also has great potential to improve the transformation frequency of recalcitrant species. The generation of transgenic plants free of antibiotic resistance markers is a major challenge. Marker-free transformation appears to be effective for the generation of marker-free transgenic plants and has the potential to improve the transformation frequency of recalcitrant species.