Abstract:
Plantlets were regenerated successfully through somatic embryogenesis of NaCl stressed (up to 350 mM) and subsequently selected, tolerant (up to 300 mM) callus lines of the aromatic grass Cymbopogon martinii (Roxb.) Wats. The NaCl tolerant callus lines were isolated, characterized and selected on the basis of their growth behaviour as well as physiological parameters (K+/Na+ ratio and proline contents) and compared with those of the wild type (control) callus lines. The regeneration potential of the NaCl tolerant callus ranged from 81.6 to 0% against 80.4 to 0% in the control lines with the NaCl level varying between 0-300 mM and 0-200 mM respectively in the medium. The embryogenic potential of NaCl tolerant callus selected even at 300 mM could be improved significantly by the incorporation of gibberellic acid (GA(3)) and abscisic acid (ABA) in the medium where, with 2 mg/l of GA(3) and 1 mg/l of ABA the highest rates of embryogenesis (44.5, 28.8 and 18.6%) were achieved against 17.5, 8.2 and 1.8% on medium devoid of GA(3), and ABA at 50, 150 and 250 mM of NaCl respectively. Complete tissue browning and subsequent death were observed at 300 mM NaCl in the differentiation medium. Plantlets regenerated from NaCl tolerant callus were transferred to soil and grown under green house conditions with about 70% transplantation success. (C) 1997 Elsevier Science Ireland Ltd.