Genetic Variation in Responses to Salt Stress in Tunisian Populations of Medicago ciliaris

Soil salinity is one of the most serious environmental factors affecting crop productivity around the world. We used a morpho-physiological approach to investigate the salt responses of four Tunisian natural populations of Medicago ciliaris. Forty-six lines of M. ciliaris were grown under a control treatment and 100 mM NaCl. We measured 11 quantitative traits of shoot and root growth during harvest. An analysis of variance showed that the variations in salt response can be explained by the effects of the population, line, treatment, and interactions between the population and treatment and the line and treatment. Most of the measured traits showed significant differences between the studied populations under the control treatment and salt stress. High to moderate broad-sense heritabilities (H-2) were noted for most of the parameters under the control treatment and salt stress, implying that salt tolerance is highly heritable. Most correlations between the measured traits under the two treatments were positive, of which the strongest correlations were recorded between characteristics related to development. The 46 studied lines formed three groups in both conditions, while their genetic structure was dependent on the treatment factor. The results from this study can provide a basis for identifying and breeding salt-tolerant lines of M. ciliaris.