Establishing a Rice Calli Subculture System With Long-term Morphogenic Potential

Abstract

This paper describes a subculture system of rice calli (cultivar J-104) that maintains the potential for long-term regeneration. We examined the effects of 2.4-D (1.0, 2.0, 3.0, 4.0 and 5.0 mg/L) and time of subculture on the morphogenesis and regeneration potential. Calli were subcultured for two years on semisolid medium, in the dark. During this time, calli with similar weight were monthly transferred to the regeneration medium, under photoperiod regime. Plant regeneration took place through two morphogenic pathways: indirect somatic embryogenesis and indirect organogenesis. The concentration of 2.4-D used in the callogenesis determined the prevalence of one path or another. In the first ten months of subculture, embryogenesis prevailed over organogenesis. However, from this point to the final stages, the shoots were organogenic. Callus lines retained their regeneration potential by organogenesis until the end of the second year, without presenting a significant number of abnormal plants. These results indicate that it is possible to maintain for two years J-104 rice callus lines potentially morphoge-nic, which can be applied to a plastid transformation protocol, specifically to the design of an efficient and long-stage selection, for reaching of homoplasmy during the callus period, before the regeneration of the plants.