Transformation and regeneration of dicotyledonous plants

The formation of crown galls on many dicotyledonous plants, as a result of Agrobacterium tumefaciens infection, has been well documented (1). The transfer of a small T-DNA region of the Ti plasmid to the nuclear genome of the plant host (2) and expression of the T-DNA growth hormone genes are responsible for the unorganized habit characteristic of crown gall tumors (3). Originally, it was thought that only dicotyledonous species could be infected, but a number of reports have recently suggested that monocotyledonous species may also be transformed by this means (4-7).