Growth and Physiological Responses and Selection of Tedera (Bituminaria bituminosa L.) Genotypes Under Salt Stress Conditions

Tedera (<i>Bituminaria bituminosa</i> L.) is a highly resilient perennial legume that maintains high forage quality under drought and poor fertility conditions with minimal inputs. Identifying salt-tolerant genotypes is crucial for rehabilitating degraded soils and promoting sustainable, low-input production systems. This study evaluated the effects of increasing salinity on the growth and physiological responses of 12 high-yielding tedera genotypes grown under five NaCl concentrations (0, 25, 50, 75, and 100 mM). Growth parameters, photosynthetic pigments, lipid peroxidation, proline amount and mineral substance contents were determined. Increasing NaCl doses caused significant decreases in plant height, leaf number, stem and root weights, while lipid peroxidation and proline accumulation increased. Several genotypes were able to maintain their chlorophyll content and growth performance even under high salinity levels, indicating potential salt tolerance. Correlation analysis indicated a significant negative relationship between the proline concentration and the chlorophyll content. G1, G2, and G3 genotypes showed the highest values when plant height (respectively, 52.23, 52.96 and 52.06 cm), leaf number (53.66, 51.53 and 47.53 per plant), and stem fresh (25.74, 24.56, and 24.44 g) and dry weights (16.78, 16.26 and 15.54 g) were considered together. In the control treatment, the contents of chlorophyll a, chlorophyll b, and carotenoids were 1.362, 0.016, and 0.006 mg g^-1, respectively, which declined to 0.726, 0.006, and 0.003 mg g^-1 at 100 mM NaCl. The average proline content increased from 1.743 µmol g^-1 in the control to 3.403 µmol g^-1 at 100 mM NaCl dose. When above-ground biomass yield, leaf number, chlorophyll content, proline content, and lipid peroxidase value are considered together, the G1 and G2 tedera genotypes, which are less affected by salinity stress, can be recommended. These findings provide a physiological basis for breeding salt-tolerant tedera cultivars suitable for saline regions of Türkiye.