RESUMEN
Conditions were optimised for efficient callus induction from seeds of four local indica rice cultivars, GR-3, GR-102, Jaya and Te-Tep. Addition of 2,4-D to MS medium at 2.5 mg/l resulted in 100% callus induction. N6 medium was superior to MS medium for callus growth, formation of embryogenic callus as well as regeneration. Cultivar Te-Tep showed highest callus growth while GR-102 the least. Addition of casein hydrolysate enhanced growth of callus but did not yield more embryogenic calli. Supplementation of MS or N6 media with proline, not only increased callus growth but also showed an increase in embryogenic callus formation. GR-102 callus was most embryogenic followed by Te-Tep, GR-3 and Jaya. Histological observation of embryogenic calli revealed the presence of pro-embryo like structures. It was also observed that calli induced on N6 medium supplemented with proline could maintain regeneration potential for a longer period as compared to other media. Cytokinins like BAP or kinetin alone could not initiate shoot formation. Regeneration frequency, and the number of shoots formed per callus increased significantly. Cultivar Te-Tep gave the best response for regeneration followed by Jaya, GR-3 and GR-102.