Simulated yield and protein responses of old and modern durum wheat in Mediterranean rainfed systems

Durum wheat (Triticum turgidum ssp. durum) is a staple crop in Mediterranean rainfed systems, where warming and more variable rainfall are expected to increase drought stress and yield risk. This study compared phenology, grain yield and grain protein of two contrasting ideotypes—five modern semi-dwarf cultivars and five old tall, late-flowering cultivars—using multi-season field data (northern Sardinia, 2013–2017) and crop modelling. The CERES-Wheat model within DSSAT (Decision Support System for Agrotechnology Transfer) was calibrated (2014–2015) and independently evaluated (2016–2017). Anthesis and maturity were simulated with high accuracy (RMSE 3–6 d; d ≥ 0.93), while grain yield agreement was moderate (RMSE ≈ 1.2 t ha⁻¹). Long-term simulations (1980–2100) driven by five climate models, three future pathways, and contrasting nitrogen inputs projected progressive warming (+1.3 to +4.5 °C) and reduced precipitation under higher-emission futures. Modern cultivars advanced anthesis more strongly (up to ∼30 d by 2100) while grain-filling duration changed little, resulting in higher simulated yields, particularly under higher nitrogen inputs (up to ∼5.9 t ha⁻¹). Old cultivars maintained lower but comparatively stable yields (around to 2.8 t ha⁻¹) and showed a slight late-century shortening of grain filling. Grain protein concentration was largely insensitive to future pathways, remaining ∼14% in old and ∼10% in modern cultivars. These results quantify a robust trade-off between productivity and grain quality and indicate that adaptation in marginal Mediterranean rainfed systems should prioritize matching cultivar group to feasible management intensity and end-use goals, with old cultivars remaining relevant where their higher protein concentration, local identity and traditional uses can be valorised through quality-oriented value chains.