Fertile plant regeneration from cryopreserved calli of Oryza rufipogon Griff. and assessment of variation in the progeny of regenerated plants.

A protocol was developed for preservation of calli of Oryza rufipogon Griff. in liquid nitrogen (-196°C). Optimal conditions for cryoprotection, pre-freezing and post-thaw recovery of calli were identified. Cryoprotectant treatment at low temperature, pre-freezing in isopropanol bath for 1 h at -70°C, rapid thawing and proper removal of cryoprotectant were critical for post-thaw survival. Genetic fidelity of the R1 plants obtained from cryopreserved, cryoprotectant-treated and untreated calli was assessed by phenotypic and molecular characterization. Comparison of phenotypic characters with seed-derived control plants showed no significant variation in the agronomic characters, but seed physical characters showed significant reduction in all the in vitro generated plants. Molecular data generated using 26 rice simple sequence repeat markers showed 4.78-7.25% change from control. Results suggested that both callus induction and cryopreservation induced heritable variations in O. rufipogon. In addition, a combination of phenotypic and molecular characterization using an appropriate marker provided better insight into genetic fidelity of recovered plants.