Optimization of in vitro culture media for improvement in yield of Navara ancient Indian medicinal rice.

Medicinally important ancient Navara rice (GI Kerala, India 2007) is a very short duration (60-70 days) variety with a yield of only 0.5 tonnes/hectare costing ~ Rs. 400/kg. It is used for indigenous treatment for chronic diseases by local and oral consumption. In this study, scutellum-derived calli were generated from mature Navara seeds and these were inoculated on different CIM-1 to CIM-5 media supplemented with 2.5 mg/l 2,4-dichlorophenoxyacetic acid. Regeneration of calli on different regeneration media RI, RII and RIII media were performed. Regeneration of 30-day-old calli on RI media showed 30%, for RII it showed no regeneration and on RIII media only 12% regeneration was obtained. The addition of glutamine and proline showed a 30-40% improvement in somatic embryogenesis. The 74-88% callus induction frequency was obtained on CIM-1 to CIM-5. The fresh weight (mg) of 30-day-old calli is CIM-2 < CIM-3 < CIM-4 < CIM-1 << CIM-5 and corresponding size shows CIM-2-CIM-3 < CIM-5 < CIM-1 < CIM-4. A negative correlation between the callus fresh weight and the regeneration efficiency was observed. In CIM-5, 20-25 days 3.4-fold increase and 25-30 days a 1.7-fold increase in fresh weight of calli is noted. The 20-day-old calli transfer to RI media shows 80% regeneration frequency and 6-7 plantlets/callus, which are twofold higher as compared with 30-day-old calli. The somatic embryogenesis and its regeneration on synthetic media provide an alternative for biotechnological intervention for yield improvement, in turn cost reduction for Navara rice.