Abstract: Inactivation of the cytokinin autonomy gene of T-DNA in broad host range Ti plasmid produces mutant T-DNA vectors suitable for insertion of foreign genes; insertion of the mutant T-DNA by an in vitro tissue culture technique or any other technique into plant cells produces genetically engineered plant cells that can be regenerated into complete plants with roots. The inactivation of the cytokinin autonomy gene disarms the Ti plasmid and produces a useful gene vector for higher plants. The inactivation of the cytokinin gene may be accomplished by techniques such as point mutation, inversion, deletion, transposition, substitution or insertion.