Evaluating Predictive Values of Various Physiological Indices for Salinity Stress Tolerance in Wheat

Soil salinity is a worldwide issue that affects agricultural production. The understanding of mechanisms by which plants tolerate salt stress is crucial for breeding varieties for salt tolerance. In this work, a large number of wheat ( Triticum aestivum and Triticum turgidum ) cultivars were screened using a broad range of physiological indices. A regression analysis was then used to evaluate the relative contribution of each of these traits towards the overall salinity tolerance. In general, most of the bread wheats showed better Na + exclusion that was associated with higher relative yield. Leaf K + /Na + ratio and leaf and xylem K + contents were the major factors determining salinity stress tolerance in wheat. Other important traits included high xylem K + content, high stomatal conductance and low osmolality. Bread wheat and durum wheat showed different tolerance mechanisms, with leaf K + /Na + content in durum wheat making no significant contributions to salt tolerance, while the important traits were leaf and xylem K + contents. These results indicate that Na + sequestration ability is much stronger in durum compared with bread wheat, most likely as a compensation for its lesser efficiency to exclude Na + from transport to the shoot. We also concluded that plant survival scores under high salt stress can be used in bread wheat as a preliminary selection for Na + exclusion gene(s).