Cytokinin Mediated Long-term, High-frequency Plant Regeneration in Rice Tissue Cultures

In Mahsuri rice callus cultures grown in light, the total amount of callus and the percentage of callus volume composed of embryogenic cells could be increased if 0.1–0.5 mg·l⁻¹ K was added to medium containing 0.5 or 1.0 mg·l⁻¹ 2,4-D. Embryogenic regions could be proliferated and maintained on the same media. E callus on initiation medium gradually produced embryoid-like structures and finally plantlets. This process could be hastened by removing E callus to a regeneration medium containing low concentrations of IAA and BAP or K. If the E callus produced by one seed were proliferated for five four-week passages on 0.5 mg·l⁻¹ 2,4-D and 0.5 mg·l^-1 K and transferred to regeneration medium, 7,318 plants could be produced from 184 g of E callus.