Induction, selection and characterization of Cr and Ni-tolerant cell lines of Echinochloa colona (L.) Link in vitro

Chromium and nickel tolerance in Echinochloa colona L. was achieved through callus culture derived from leafbase, leaf tip and mesocotyl explants on Murashige and Skoog (1962) medium supplemented with 0.5 mg · L−1 BA, 3.0 mg · L−1 2,4-D and 1.5 mg · L−1 chromium plus 2.0 mg · L−1 nickel. Tolerant calli showed vigorous growth in medium containing 1.5 mg · L−1 chromium or 2.0 mg · L−1 nickel or 1.5 mg · L−1 chromium plus 2.0 mg · L−1 nickel. Biochemical studies on the basis of activities of peroxidase, catalase as well as estimation of chlorophyll and protein were more in tolerant calli than non-tolerant one. SDS-PAGE studies indicate that there were specific proteins (20.8, 27.6, 30.8, 45.2, 57.6, 63.4, 74.2, 80.6 and 95.2 kDa) appeared in chromium- and nickel-tolerant calli as compared with control. The accumulation of Cr- and Ni- in the tolerant callus was increased significantly with the increase in Cr- and Ni-concentration in the medium. Plant regeneration via somatic embryogenesis was achieved in both tolerant and non-tolerant calli on MS medium supplemented with 1.0-1.5 mg · L−1 BA, 0.5-1.5 mg · L−1 Kn and 0.25-0.5 mg · L−1 NAA. Somatic embryo derived plantlets were established in the greenhouse and bearing normal growth. This study will help in the selection of metal tolerant plants which might be used for phytoremediation programme.