Investigating the In vitro Regeneration Potentiality of Three High Yielding Indica Rice (Oryza sativa L.) Varieties

Aims: An efficient and reproducible In vitro regeneration protocol is vital for varietal improvement research. The current research was conducted to optimize the callus induction, shoot and root regeneration of three indica rice varieties.

Place, Duration and Design of Study: The experiment was conducted in the tissue culture and biotechnology laboratory of the department of Genetics and Plant Breeding of Bangladesh Agricultural University using completely randomized experimental design.

Methodology: Dehusked mature seeds of three indica rice varieties namely, BRRI dhan28, BRRI dhan29 and BINA dhan6 were cultured In vitro in MS medium supplemented with different concentrations and combinations of phytohormones.

Results: The callus induction ranged from 14 - 84% which showed a general increasing trend with the increase in the concentration of 2,4-Dichlorophenoxyacetic acid (2,4-D) starting from 1.0 mg L-1 till 2.5 mg L-1. A further increase in the concentration of 2,4-D to 2.5 mg L-1, however, decreased the percentage of callus induction in all three varieties. MS medium supplemented with 2.5 mg L-1 2,4-D and 0.5 mg L-1 6-Benzylaminopurine (BAP) was better than any other composition for callus induction. For size of callus and nature of callus, however, MS medium supplemented with 2.0 mg L-1 2,4-D and 0.5 mg L-1 BAP was found to perfume best. The highest percentage of callus induction was observed in the variety BRRI dhan29 (84%) followed by BRRI dhan28 (74%). Almost all the varieties produced yellowish and compact calli except BINA dhan6 which produced creamy and friable calli. The desiccation treatment has shown to increase size but decrease the compactness of the callus. The differences are, however, not statistically significant. MS medium supplemented with 0.6 mg L-1 1-Naphthaleneacetic acid (NAA) and 6 mg L-1 Kinetin (Kn) showed highest shoot regeneration in BRRI dhan29 (85%) followed by BRRI dhan28 (60%). Higher frequency of root formation was observed in all three varieties using Indole-3-butyric acid (IBA). The survival rate of the plantlet in acclimatization chamber (96%) and in field condition (93.33%) was higher for BRRI dhan29. BINA dhan6 has shown the least regeneration potentiality for all the aforementioned traits.

Conclusion: Of the three varieties, BRRI dhan29 and BRRI dhan28 has shown higher regeneration potentiality. This optimized protocol will thus be useful in genetic improvement of these varieties using biotechnological manipulations.