Quantifying the three main components of salinity tolerance in cereals

Salinity stress is a major factor inhibiting cereal yield throughout the world. Tolerance to salinity stress can be considered to contain three main components: Na⁺ exclusion, tolerance to Na⁺ in the tissues and osmotic tolerance. To date, most experimental work on salinity tolerance in cereals has focused on Na⁺ exclusion due in part to its ease of measurement. It has become apparent, however, that Na⁺ exclusion is not the sole mechanism for salinity tolerance in cereals, and research needs to expand to study osmotic tolerance and tissue tolerance. Here, we develop assays for high throughput quantification of Na⁺ exclusion, Na⁺ tissue tolerance and osmotic tolerance in 12 Triticum monococcum accessions, mainly using commercially available image capture and analysis equipment. We show that different lines use different combinations of the three tolerance mechanisms to increase their total salinity tolerance, with a positive correlation observed between a plant's total salinity tolerance and the sum of its proficiency in Na⁺ exclusion, osmotic tolerance and tissue tolerance. The assays developed in this study can be easily adapted for other cereals and used in high throughput, forward genetic experiments to elucidate the molecular basis of these components of salinity tolerance.