IN-VITRO SELECTION AND CHARACTERIZATION OF NI-TOLERANT CALLUS LINES OF SETARIA-ITALICA L

Nickel tolerant callus lines of Setaria italica L. were developed from callus cultures grown on MS medium supplemented with 0.5 mg.dm(-3) ki netin + 2.0 mg.dm(-3) 2,4-D + 2.0 mg.dm(-3) Ni+2. Standard growth para meters such as callus fresh and dry weight, growth tolerance index wer e: used as indicators of nickel toxicity. Measurements as early as 2 w eeks after the beginning of the treatments did not yield consistent re sults. However, growth tolerance index at 4, and 8 weeks after the beg inning of treatments yielded significant differences among the non-tol erant rant and tolerant calli. The tolerant calli has enhanced growth at 2.0 mg.dm(-3) Ni+2 while non-tolerant calli showed a reverse trend in growth in the presence of 2.0-2.5 mg.dm(-3) of nickel. The tolerant calli differentiated into mass of embryogenic calli within 4 weeks of culture which could be maintained for prolonged period without loss o f regenerative capacity.