Physiological and Biochemical Responses of Willow (Salix spp.) Clones to Salinity Stress in Semi-Arid Conditions: Identifying Salt-Tolerant Genotypes for Sustainable Land Use

Salinity stress presents a significant challenge to plant productivity, especially in semi-arid regions where soil degradation intensifies due to climate change and unsustainable irrigation practices. This study evaluated ten willow (Salix spp.) clones exposed to increasing irrigation salinity levels (4–16 dS/m) to investigate their physiological and biochemical responses over a 105-day period. Key stress indicators—including relative water content (RWC), water potential (Ψw), osmotic potential (Ψs), relative stress injury (RSI), proline accumulation, lipid peroxidation (MDA), and antioxidant enzyme activities (SOD, POD)—were measured to assess clone performance. Clone 131/25 consistently outperformed the others, showing higher RWC, less negative Ψw and Ψs, lower RSI and MDA levels, and increased proline, SOD, and POD activities. Clones J799 and SI-64-017 also displayed strong adaptive traits. These genotypes demonstrated superior osmotic adjustment, reduced oxidative stress, and maintained chlorophyll content under salinity, indicating the presence of effective tolerance mechanisms. Correlation analysis confirmed strong positive relationships between survival, growth, proline, and antioxidant activity, as well as negative correlations with RSI and Na⁺/K⁺ ratio. The results identify 131/25, J799, and SI-64-017 as promising candidates for cultivation on salt-affected lands and for use in agroforestry, bioenergy, and ecological restoration programmes. These findings support their deployment in climate-resilient, sustainable land management in saline-prone semi-arid regions