Unlocking salt tolerance from Fertile Crescent wild barley: evolutionary and physiological mechanisms in introgressed lines

uptake with effective tissue tolerance (likely via enhanced vacuolar sequestration), balanced osmotic adjustment to maintain hydration with minimal metabolic cost, and efficient antioxidant responses that avoided defense-yield penalties seen in wild parents. These integrated mechanisms arose from recombining adaptive alleles from multiple wild origins, with Iranian germplasm contributing strongly. A composite selection index based on these physiological traits effectively distinguished tolerant genotypes and correlated with yield stability. Our findings demonstrate that salt tolerance in barley results from balanced coordination of physiological processes rather than maximal defensive activation. Multi-origin wild introgression offers a powerful approach to restore ancestral resilience while preserving agronomic performance.