Effect of NaCl on in vitro plant regeneration from embryogenic callus cultures of 'cv IR 64' indica rice ( Oryza sativa L.)

In vitro experiments were conducted to assess the effect of salt stress on callus induction, survival, fresh weight, regeneration, proline level and total protein content in salt sensitive indica rice cv. IR 64. For callus induction and regeneration, seeds and calli were subjected to 25, 50, 75 and 100 mM NaCl mediated salt stress which caused significant reduction in proliferation when compared to the control. Gradual reduction in regeneration was observed with increasing salt concentrations (25 to 100 mM). The relative regeneration was maximum at 50 mM. Similarly, a significant increase in proline content (6.5 fold in callus culture and 9.2 fold in the leaves) was observed at 50 mM NaCl after 30 days. However, the adverse effect of salt was more pronounced on total protein content, except at 50 mM. These results suggest that proline accumulation is an index of salinity tolerance and this important international variety can be genetically manipulated to develop salinity tolerant crop. Key words: Abiotic stress, callus proliferation, proline assay, salinity, total protein.