Plant regeneration in different genotypes of indica rice

Of 10 indica rice varieties assessed, Annada showed the best in vitro culture response in respect of callus induction, plantlet regeneration and number of plantlets/seed callus. Other high yielding varieties, viz. Kasturi, IR 72 and Karnal Local, also displayed appreciable performance. Callus induced and proliferated in dark and gave high plantlet regeneration and more plantlets/seed callus across genotypes. Among three shock treatments, viz. heat (37 °C for overnight), cold (4 °C for over night) and dehydration, dehydration significantly enhanced the plantlet regeneration and number of plantlets/seed callus. Of 3-dehydration treatments (6, 12 and 24 h duration), the maximum plantlet regeneration and number of plantlets/seed callus were observed in the calli dehydrated for 12 h. Of three tested media, viz. MS, LS, and N 6, MS emerged the best for callus induction, plantlet regeneration and number of plantlets/seed callus. In contrast, among the modified media formulations, modified N6 [5 m M (NH 4)2 SO 4] produced maximum plantlets/seed callus across varieties. Increased (5 mM) (NH 4)2SO 4 content in the medium was found to be better than the higher dose of KNO 3 or its normal level in the respective media formulations. Across genotypes, 2 mg L -1 2,4-D in the callus induction medium (CIM) was the most suitable for callus induction. However, 2,4-D in combination with other growth regulators, such as 2 mg L -1 2,4-D and 1 mg L -1 Kn, performed better. In regeneration medium (RM), 2 mg L -1 BAP with 1 mg L -1 Kn and 0.5 mg L -1 NAA, or 2 mg L -1 BAP with 0.5 mg L -1 NAA, were optimum for the maximum plantlet regeneration. Across varieties, coconut water (10%) was found to be the most effective to enhance the in vitro culture response as evident from prolific callus induction, increased plantlet regeneration and more plantlets/seed callus.