Inducible isopentenyl transferase as a high-efficiency marker for plant transformation

Overexpression of the isopentenyltransferase gene (ipt) from the Ti-plasmid of Agrobacterium tumefaciens increases cytokinin levels, leading to genera tion of shoots from transformed plant cells. When combined with a dexametha sone-inducible system for controlling expression, ipt expression can be use d to select for transgenic regenerants without using an antibiotic-resistan ce marker. The combined system allows efficient cointroduction of multiple genes (in addition to ipt) and produces transgenic plants without morpholog ical or developmental defects.