Efficient callogenesis and regeneration of Japonica rice varieties from mature seeds

The present study was conducted to optimize a protocol for high efficiency embryogenic callus induction and regeneration in japonica rice. The dehusked seeds of two varieties namely Duggu and K 332 were subjected to treatment with mercuric chloride (0.1%) and sodium hypochloride (4%) for different durations and it was found that seed explants treated with 0.1% HgCl₂ for 8 minutes resulted in least contamination with maximum survival percent of cultures of K 332 and Duggu. The sterilized seeds were inoculated on MS medium with 2,4-D (2.0-4.0 mg/l) and BAP (0.5-1.0 mg/l) for callus induction and regeneration was attempted on MS medium supplemented with NAA (0.2-0.5 mg/l) and BAP (2.0-4.5 mg/l) in presence or absence of proline (50mg/l). Maximum callus induction (96.07%) of K 332 was obtained in MS medium supplemented with 2,4-D (2.5 mg/l) and BAP (1.0 mg/l) while in Duggu maximum callus induction (83.37%) was achieved in presence of 2,4-D (3.5 mg/l) and BAP (1.0 mg/l). Maximum callus regeneration frequency (67.7%) was obtained in K 332 in MS medium having BAP (2.5 mg/l) and NAA (0.4 mg/l) while maximum callus regeneration frequency (47.7%) was obtained in variety Duggu in presence of BAP (2.5 mg/l) and NAA (0.4 mg/l). Further, it was observed that presence of proline (50 mg/l) was beneficial for regeneration.