Improvement of the cultivation of rice (Oryza salivaL.) protoplasts isolated from suspension cultures led to their division at a frequency of 5 to 10. Rapidly growing colonies were obtained on a hormone-free medium whenAgrobacterium tumefaciensspheroplasts were introduced into the protoplasts by polyethylene glycol treatment. Opines corresponding to the strains ofA. tumefaciensused for the spheroplast treatments were detected in some of these colonies at a frequency of about 10−4. Using radioactive precursors, 14C-α-ketoglutaric acid and 3H-arginine, activities of nopaline synthase, a marker enzyme of nopaline-type crown gall, were also detected in some of these clones. These results show that the rice cells were transformed by Ti plasmid introduced by the spheroplast meth
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