Plant regeneration from tissue cultures of Pokkali rice is promoted by optimizing callus to medium volume ratio and by a medium-conditioning factor produced by embryogenic callus

The frequency of plant regeneration from seed-derived Pokkali rice callus has been substantially increased. Four conclusions were drawn from the study: (1) Non-embryogenic callus consisting of elongated, highly-vacuolated cells did not produce regenerated plants. Embryogenic callus consisting of small, non-vacuolated cells produced somatic embryos and regenerated plants. (2) The numbers of plants could be markedly increased by optimizing a medium for embryogenic callus production and a second medium for plant regeneration from embryogenic callus. (3) The optimization of callus to medium volume ratio of 6.5 mg embryogenic callus per 1.0 ml of medium significantly increase plant production on regeneration medium. (4) A further significant increase was obtained by using regeneration medium previously conditioned for one or two weeks by optimal amounts of embryogenic callus. At present, the callus derived from a single seed in six months could theoretically be used in the seventh month to produce 127500 plants.This research was supported by the Agency for International Development under Contract No. AID/DSAN-C-0273