In vitro selection of NaCl-tolerant callus lines and regeneration of plantlets in a bamboo (Dendrocalamus strictus Nees.)

Sodium chloride-tolerant plantlets of Dendrocalamus strictus were regenerated successfully from NaCl-tolerant embryogenic callus via somatic embryogenesis. The selection of embryogenic callus tolerant to 100 mM NaCl was made by exposing the callus to increasing (0-200 mM) concentrations of NaCl in Murashige and Skoog medium having 3% (w/v) sucrose, 0.8% (w/v) agar, 3.0 mg l(-1) (13.6 muM) 2,4-dichlorophenoxyacetic acid (2,4-D), and 0.5 mg l(-1) (2.3 muM) kinetin (callus initiation medium). The tolerance of the selected embryogenic callus to 100 mM NaCl was stable through three successive transfers on NaCl-free callus initiation medium. The tolerant embryogenic callus had high levels of Na+, sugar, free amino acids, and proline but a slight decline was recorded in K+ level. The stable 100 mM NaCl-tolerant embryogenic callus differentiated somatic embryos on maintenance medium [MS medium + 3% sucrose + 0.8% agar + 2.0 mg l(-1) (9.0 muM) 2,4-D + 0.5 mg l(-1) (2.3 muM) kinetin] supplemented with different (0-200 mM) concentrations of NaCl. About 39% of mature somatic embryos tolerant to 100 mM NaCl germinated and converted into plantlets in germination medium [half-strength MS + 2% sucrose + 0.02 mg l(-1) (0.1 muM) alpha-naphthaleneacetic acid + 0.1 mg l(-1) (0.49 muM) indole-3-butyric acid] containing 100 mM NaCl. Of these plantlets about 31% established well on transplantation into a garden soil and sand (1:1) mixture containing 0.2% (w/w) NaCl.