Induction of somatic embryo and plantlet regeneration from mature caryopsis culture under NaCl-salt stress conditions in traditional Indian black rice (Oryza sativa L.)

This study was conducted to establish an efficient in vitro regeneration technique for the induction of somatic embryo and plantlet regeneration under NaCl-salt stress conditions in black rice ( Oryza sativa . L., cv Co57), a traditional Indian cereal food. Embryogenic calli were obtained from mature caryopsis culture on Murashige and Skoog (1962) medium fortified with 2,4-dichlorophenoxyacetic acid (2.0mg/L) either alone or in combination with various concentrations of NaCl (10mM, 25mM, 50mM, and 100mM) in order to induce the salt tolerant somatic embryo differentiation. Furthermore, embryogenic calli were found to show shoot regeneration on MS-medium fortified with 2.0mg/L of 6-benzylaminopurine (BAP) in combination with 0.5mg/L of α-naphthaleneacetic acid (NAA) and in presence of NaCl (10mM, 25mM, 50mM, and 100mM). Significantly, the high concentration (150mM) of NaCl was proved to be lethal for both somatic embryogenesis as well as plantlets regeneration. Moreover, the low frequency (40.3%) of somatic embryogenesis and minimum number of salt tolerant somatic embryos per callus (3.2±0.1) was recorded with the caryopsis explants that were treated with the high concentration (100mM) of NaCl-salt added embryo induction medium. Significantly, low frequency of salt-tolerant plantlets regeneration (25%) and minimum number of plantlets per embryogenic callus (1.5±0.1) was recorded in the embryogenic callus that was treated with 100mM of NaCl in regeneration medium containing BAP (2.0mg/L) in combination with NAA (0.5mg/L). Further, salinity tolerant plantlets were transferred to soil and gradually acclimatized under growth chamber conditions. This study thus offers a suitable technique for production of salt tolerant black rice, an alternative approach for the traditional Indian black rice crop improvements.