Introduction
Crown vetch (Securigera varia) is considered one of the most suitable perennial forage species for cultivation in arid and semi-arid regions due to its high adaptability to diverse environmental conditions and favorable forage characteristics. Salinity stress is one of the most critical limiting factors affecting forage yield and quality in such regions. Owing to its deep root system, strong regrowth ability, and relatively high drought tolerance, this species can grow in areas where many other forage crops fail to survive. However, soil salinity remains a major abiotic stress that severely restricts the growth, quantity, and quality of forage production. Therefore, understanding the responses of different S. varia ecotypes to salinity stress is essential for identifying tolerant and high-quality genotypes and ensuring sustainable forage production.
Materials and Methods
The experiment was conducted in 2024 in the greenhouse of the University of Kurdistan, Iran, using a factorial arrangement based on a completely randomized design with three replications. The first factor consisted of ten Securigera varia ecotypes (Nahavand, Hamedan, Semnan, Ilam, Kermanshah, Paveh, Sanandaj, Marivan, Saqez, and Sarvabad), while the second factor included four salinity levels (0, 100, 200, and 300 mM NaCl). Morphological and quantitative traits, including shoot and root dry weight, plant height, and root length, as well as forage quality parameters such as crude protein, crude fiber, acid detergent fiber, neutral detergent fiber, digestible dry matter, and total ash, were measured.
Results and Discussion 
The interaction between salinity levels and ecotypes had a significant effect on the morphological traits, quantity, and quality crown vetch. At 100 mM salinity, shoot and root dry weight, plant height, root length, crude protein, and digestible dry matter increased, whereas these traits decreased at higher salinity levels (200 and 300 mM). The highest crude protein content (24.70%) was recorded in the Nahavand and Saqez ecotypes at 100 mM, while the lowest (6.93%) was observed in the Ilam ecotype at 300 mM. Crude fiber reached its maximum (31.79%) in the Paveh ecotype at 300 mM and the minimum (10.11%) in the Hamedan ecotype at 100 mM. Acid detergent fiber and neutral detergent fiber were highest (83.05% and 85.03%) in the Paveh ecotype at 300 mM and lowest (21.01% and 31.55%) in the Nahavand and Sarvabad ecotypes at 100 mM. Digestible dry matter was highest (76.78%) in the Nahavand ecotype at 100 mM and lowest (24.78%) in the Ilam ecotype at 300 mM. Total ash content reached its maximum (15.44%) in the Paveh ecotype at 300 mM and minimum (7.99%) in the Hamedan ecotype at 100 mM.
Conclusion
Mild salinity (100 mM) promoted the growth and forage quality of crown vetch, whereas higher salinity levels significantly impaired these traits. Among the evaluated ecotypes, the Nahavand ecotype exhibited the greatest salinity tolerance and consistently produced superior forage quality compared with the other ecotypes. These findings indicate that the Nahavand ecotype is the most suitable candidate for cultivation in saline environments, where it can help maintain both forage yield and quality. Overall, salinity is a major factor influencing the growth and forage quality of crown vetch, underscoring the importance of selecting salt-tolerant ecotypes to enhance productivity and support sustainable forage production under saline conditions.