Evaluation of salt tolerance in rice cultivars at seedling stage in hydroponic medium through IC50 method

Salt tolerant cultivars of rice are continuously being developed for suitability of their cultivation in salt affected lands that cause significant loss in the crop yield. Testing of salt tolerance of a large number of breeding lines generated after crossing and selfing is a major constrain in the development of salt tolerant cultivars. The present study describes a laboratory-based method of testing salt tolerance of the breeding lines at the seedling stage. Shoot growth inhibition data were generated for five rice cultivars after hydroponic exposure of the 5 days old seedlings to 0.5%, 1.0%, 1.5% and 2.0% NaCl for 24, 48 and 72 h. The 72 h IC 50 values for NaCl varied from 0.91% (156 mM) for the salt-sensitive Naveen to 1.8% (300 mM) for the salt-tolerant Pokkali. The IC 50 values clearly demonstrated difference in salt-tolerance/sensitivity of the rice cultivars, and hence the method can be used for testing salt tolerance of the breeding lines in the shortest possible time. Moreover, the method provides a quantitative value, rather than mere phenotypic observations being followed in the prevailing method of screening of salt tolerance of breeding lines.