The development of an efficient tissue culture protocol for somatic embryo would facilitate the genetic modification in
breeding program. The present study describes the reproducible protocols for three wetland Malaysian rice cultivars
(MR232, MR220 and MR220-CL2) and upland rice (Bario) via somatic embryogenesis. In the present study, four preheat treatments (35, 40, 45 and 50°C) were applied to mature seeds with different imbibition periods (3, 5 and 7 days)
prior to culture on MS media with 3 mg/L 2,4-D. The results showed that the cultivars exhibited the highest callus
induction percentage from 45°C pre-heated seeds and 3 days imbibition (100%, 96%, 100% and 95% for MR232, MR220,
MR220-CL2 and Bario, respectively). Callus was induced early ranging from 3 to 12 days compared to without pre-heat
treatment. The regeneration efficiency for MR220 and MR220-CL2 cultivars was significantly higher compared to the
control treatment. However, both 45°C and 25°C (control) treatments produced higher plantlet regeneration for MR232
and Bario. This study observed that pre-heat treated seeds prior to callus induction did promote callusing and hence
regeneration. These findings can be used to establish a suitable protocol for the in vitro regeneration system for several
genetic improvements in the numerous stress tolerances of Malaysian rice.