Embryogenic cell suspension was obtained from the calli developed from mature seeds of rice Roncarolo (Oryza sativa L., a japonica cultivar from Italy ). The protoplasts were isolated from cell suspension by treatment of enzyme mixture and suspended in the solution containing 0.56% (w/v) MgCl_2·6H_2O, 0.10%(w/v) MES and 0.4 mol/1, pH 5.6 mannitol to a final density of 2×10~5 / ml. The transformation vector used was pHP23 carrying the NPT 11 gene which encodes resistance to the antibiotics of kanamycin and G-418. The plasmid DNA was added to the protoplast solution to make final concentration at 4×10~(-4) μg DNA/ml. The mixture was incubated for 15 min at room temperature to allow sufficient contact between the DNA and the plasma membrane of protoplasts. Then, 40% PEG-6,000 solution was slowly and gently added into the mixture to bring the final PEG concentration to 25%(w/v). After another 15 rain of incubation, the PEG was washed away with solution of 2.9%(w/v) KC1, 5.56%(w/v) MgCl_2·6H_2O and 4.14 Embryogenic cell suspension was obtained from the calli developed from mature seeds of rice Roncarolo (Oryza sativa L., a japonica cultivar from Italy). The protoplasts were isolated from cell suspension by treatment of enzyme mixture and suspended in the solution containing 0.56% (w / v) MgCl 2 · 6H 2 O, 0.10% (w / v) MES and 0.4 mol / 1, pH 5.6 mannitol to a final density of 2 × 10 ~ 5 / ml The transformation vector used was pHP23 carrying the NPT 11 gene which encodes the plasmid was incubated for 15 min at room temperature to allow the antibiotics of kanamycin and G-418. The plasmid DNA was added to the protoplast solution to make the final concentration at 4 × 10 ~ (-4) μg DNA / ml. sufficient contact between the DNA and the plasma membrane of protoplasts. Then, 40% PEG-6,000 solution was slowly and gently added into the mixture to bring the final PEG concentration to 25% (w / v). After another 15 min of incubation, the PEG was washed away with solution of 2.9% (w / v) KCl, 5.56% (w / v) MgCl _2 · 6H_2O and 4.14