RESUMO
With the purpose of increasing the embryogenesis regeneration process in vitroplants obtained from somatic embryos of the indica rice variety CR-5272 (Oryza sativa L.), two independent experiments were performed. The first experiment consisted in the effect of combination of three concentrations of the gelling agent PhytagelTM (1.8, 2.4, and 3 gL-1) and four 2,4-D concentrations (2.26, 4.52, 6.78, and 9.05 m M) on the induction and subsequent regeneration of embryogenic calli. On the second experiment, the pre-regeneration phase was modified; calli were subjected to darkness or diffuse light conditions for one, two, and three weeks. In embryogenesis induction, 35% calligenesis was obtained using the MS culture medium supplemented with 6.78 m M of 2,4-D and 2.4 gL-1 PhytagelTM , whereas on the control treatment (MS medium supplemented with 9.05 m M of 2,4-D and 3 gL-1 PhytagelTM ) 24% calligenesis was obtained. In addition, regeneration percentages were improved (22% and 16% for calli induced with the above treatments, respectively). Furthermore, in light exposure experiments, the best result was obtained by exposing the embryogenic calli to darkness for one week in pre-regeneration, followed by direct light exposure during the regeneration phase