Efficient plant regeneration from cell suspension cultures of rice (Oryza sativa L)

The effects of various components of culture media and culture conditions on plantlet regeneration in cell suspension cultures of rice (Oryza sativa L.) were studied. It was found that plantlet regeneration was affected by the concentrations of medium components such as plant growth regulators, carbohydrates, inorganic nitrogen salts, and osmoticum in the NG medium (Chu et al., 1975). Addition of 0.1 mg/L NAA in combination with 0.1 mg/L kinetin improved regeneration. A low level of sucrose (7 g/L) promoted regeneration, and an increased sucrose level (above 20 g/L) was highly inhibitory. A concentration of KNO3 twice as high as that of the N6 medium resulted in a doubling in the number of regenerated plantlets. Although sorbitol was necessary for plantlet regeneration, mannitol inhibited regeneration. This contradictory effect between common osmotica on regeneration suggests that sorbitol was physiologically rather than just osmotically active. In addition to the components of the regeneration medium, culture conditions such as medium volume and volume of culture vessel were found to be important factors affecting regeneration. Culture in 300 mL flasks containing 30 mL of medium resulted in a two-fold increase in the number of regenerated plantltets in comparison with culture in 100 mt flasks containing 20 mt of medium. Under optimum conditions, more than 200 plantlets per 20 mg of cell clusters regenerated in suspension cultures in 6 weeks.