Variation in yield potential and salt tolerance of selected cultivars and natural populations of Trifolium repens L

Abstract

The effects of NaCl (0-60 mol m-3) on growth rates, dry matter production, leaf expansion, photosynthesis and tissue ion concentrations were evaluated in 10, widely sourced cultivars and five natural populations of Trifolium repens. Shoot dry matter in all cultivars was significantly reduced at NaCl concentrations greater than 20 mol m-3. The rate of yield decline was greater in those cultivars which had the highest yield under non-saline conditions. In all cultivars, shoot concentrations of Na and Cl increased significantly with increasing external NaCl concentrations, but the response of individual cultivars differed. Differences in the capacity to control the uptake and distribution of Na and Cl into the shoot were related to differences in salt tolerance. Four cultivars (Haifa, Irrigation, Ladino and Tamar), representing extremes in relative salt tolerance, were studied in detail. There were no significant differences in root growth or in the concentrations of Na and Cl in the roots between these cultivars when grown at 0 to 60 mol m-3 NaCl. Rates of leaf expansion and petiole elongation were significantly reduced by NaCl in Ladino and Tamar, which had lower salt tolerance, but were not reduced greatly in Haifa and Irrigation, the two cultivars with higher tolerance. Individual leaf photosynthesis rates were not sensitive to NaCl and did not differ between cultivars. There were no significant differences in shoot yields or in shoot ion concentrations between five populations of T. repens, collected from the Mediterranean Region, and the control cultivar Haifa, although two populations (9028 and 9494) produced more dry matter at 60 mol m-3 NaCl. The plant-to-plant variation for all measured characters was large within both populations and cultivars. This study showed that genotypes which have greater salt tolerance or greater yield potential under non-saline conditions can be selected in order to maximize the yield of T. repens under moderately saline conditions.