Abstract
Salinity stress remains one of the world's oldest and the most serious environmental problem, which substantially hampers crop productivity in arid and semi arid areas. This problem has been addressed by expensive and energy depleting soil reclamation measures. However, a cheaper sustainable alternative lies in the development of salt tolerant crop cultivars. In this study, we tested salinity tolerances of 98 wheat accessions originating from Pakistan, India and Mexico from measurements of their shoot and root growth in cultures containing 0, 10 and 15 dS/m of NaCl. Genotypic responses were compared from measures of absolute and relative salt tolerances. Differential growth reductions to increased salinity were observed in the wheat accessions with those originating from Mexico exhibiting significantly greater salinity tolerances overall than those originating from Pakistan. No significant correlations were found between plant salinity tolerances and their vigour as measured by relative growth rates in controls; with relative growth rates of different genotypes grouped on the basis of different geographic origin and different genes of various stresses also not differing significantly from each other. Estimated broad-sense heritabilities indicated that phenotypic variance exceeded that of genotypic by nearly two orders of magnitude. These findings indicate that the genetic improvement of salt tolerance in wheat through selection will be problematic due to masking effects of the environment, and imply rigorous and careful selection of salt tolerant accessions.