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The ability of wheat to maintain a low sodium concentration ([Na⁺]) in leaves correlates with improved growth under saline conditions^,. This trait, termed Na⁺ exclusion, contributes to the greater salt tolerance of bread wheat relative to durum wheat^,. To improve the salt tolerance of durum wheat, we explored natural diversity in shoot Na⁺ exclusion within ancestral wheat germplasm. Previously, we showed that crossing of Nax2, a gene locus in the wheat relative Triticum monococcum into a commercial durum wheat (Triticum turgidum ssp. durum var. Tamaroi) reduced its leaf [Na⁺] (ref. ). Here we show that a gene in the Nax2 locus, TmHKT1;5-A, encodes a Na⁺-selective transporter located on the plasma membrane of root cells surrounding xylem vessels, which is therefore ideally localized to withdraw Na⁺ from the xylem and reduce transport of Na⁺ to leaves. Field trials on saline soils demonstrate that the presence …