Rapid regeneration and ploidy stability of 'cv IR36' indica rice (Oryza Sativa. L) confers efficient protocol for in vitro callus organogenesis and Agrobacterium tumefaciens mediated transformation.

BACKGROUND

Cereal crops are the major targets for transformation mediated crop improvement and IR36 is an early maturing, high yielding, insect and disease resistant rice variety however, it is abiotic stress sensitive. Hence, development of an efficient and reproducible micropropagation system via somatic embryogenesis and Agrobacterium tumefaciens mediated transformation is prerequisite to develop abiotic stress tolerant IR36. Further, Genetic stability of analysis of plantlets through RAPD and ISSR and Ploidy level through Flow cytometry (FCM) measurement of 2C DNA content is necessary for future application of transformed IR36.

RESULTS

In this study, Mature seeds inoculated on (Murashige and Skoog) MS medium with 11.31 μM 2, 4-dichlorophenoxyacetic acid (2, 4-D) and 0.3 μM Kinetin (Kn) had highest callus induction frequency (98%). The highest regeneration frequency (80%) was observed in MS + 13.28 μM Benzyladenine (BA) with 8.06 μM α-naphthalene acetic acid (NAA). Randomly Amplified Polymorphic DNA (RAPD), Inter Simple Sequence Repeat (ISSR) and Flow Cytometry (FCM) analysis showed no significant variation in the 2C DNA (0.81 pg/2C) content and Ploidy level between wild type IR36 and in vitro maintained rice lines. Of the various OD bacterial culture, an optimum OD of 0.4 and inoculation duration of 10 min resulted in efficient Agrobacterium-mediated transformation. β-glucuronidase activity was maximum in callus (99.05%).

CONCLUSIONS

These results described here confirm the reliability of this protocol for micropropagation and delivery of desirable gene using A. tumefaciens into indica rice.