Durum wheat ideotypes in Mediterranean environments differing in water and temperature conditions

Ideotypic characteristics of durum wheat associated with higher yield under different water and temperature regimes were studied under Mediterranean conditions. Six semi-dwarf cultivars with contrasting agronomic performance were grown during two consecutive years under winter-planted rainfed and winter-planted support-irrigation conditions and a late-planting trial under support irrigation, at the INIA station of Colmenar de Oreja (Madrid). Different traits were assessed to inform on: water status, root performance, phenology, photosynthetic capacity, crop growth, grain yield and agronomic yield components. Under support irrigation and normal planting, genotypes with higher grain yield exhibited better water status (lower δ¹³C and canopy temperature), assimilation of more superficial water (higher δ¹⁸O), earlier heading and greater plant height and ear density. Under water-limited conditions (rainfed), the best genotypes also exhibited better water status (lower δ¹³C) and earlier heading, but higher specific root length with extraction of water from deeper soil layers (lower δ¹⁸O), more efficient N metabolism (higher δ¹⁵N and NBI) and consequently stronger growth (plant height and NDVI), and greater ear density and thousand grain weight. Under warmer conditions (late planting), the best genotypes also exhibited better water status (lower δ¹³C) and greater plant height and photoprotective mechanisms (higher flavonoid content and lower chlorophyll content). However, the strong differences in drought between consecutive years determined other specific ideotypic traits within each of the three growing conditions and the particular year. Our study suggests specific ideotypes when breeding durum wheat under different agronomic scenarios, but also stresses that interannual variation in water conditions, typical of Mediterranean conditions, should be taken into account.