In vitro selection of NaCl tolerant callus lines of Cymbopogon martinii (Roxb) wats

Abstract

Sodium chloride tolerant callus lines of Cymbopogon martinii (Roxb.) Wats were obtained by exposing the callus to increasing concentrations of NaCl (0-350 mM) in the MS medium. The tolerant lines grew better than the sensitive wild-type lines in all concentrations of NaCl tested up to 300 mM. Callus survival and growth were completely inhibited resulting in tissue browning and subsequent death at 350 mM NaCl. The selected lines retained their salt tolerance after 3-4 subcultures on salt-free medium indicating the stability of the induced salt tolerance. The growth behaviour, the Na+, K+ and proline contents of the selected callus lines were characterised and compared with those of the NaCl sensitive lines. The Na+ levels increased sharply, while the K+ level declined continuously with the corresponding increase in external NaCl concentrations in both lines but the NaCl-tolerant callus lines always maintained higher Na+ and K+ levels than that of the sensitive lines. The NaCl-selected callus line accumulated high level of proline under salt stress. The degree of NaCl-tolerance of the selected lines, was in negative correlation with the K+/Na+ ratio and in positive correlation with proline accumulation. (C) 1997 Elsevier Science Ireland Ltd.