Wheat cultivars can be screened for NaCl salinity tolerance by measuring leaf chlorophyll content and shoot sap potassium

An efficient screening procedure is essential for breeding for salinity-tolerant crops, but there is no consensus regarding the best approach. While some authors argue that the selection of tolerant genotypes should be undertaken under field conditions, others believe that field-based trials for salinity tolerance is problematic due to confounding environmental factors. Also, the choice of specific physiological trait(s) used is often subjective, frequently depending on the 'personal philosophy' of the researcher. In this work, we undertook an unbiased assessment of a multitude of physiological and agronomical parameters in an attempt to find a combination that would satisfy two main criteria: (1) be relatively easy and quick to measure; and (2) possess a high predictive power. Fourteen physiological and agronomical traits were measured and analysed using various statistical methods (multiple regression, cluster analysis, principal component analysis). Our results indicate that measuring just two parameters; changes in the chlorophyll content in the 5th leaf after 6 weeks of NaCl treatment, and shoot sap K+ content in control plants, measured at the same time, satisfied these requirements and could be used as efficient screening tools in wheat breeding programs. Interestingly, salt tolerance was associated with lower but not higher K+ content in control plants. The physiological mechanisms involved are discussed.