Agronomic and physiological responses of Chinese facultative wheat genotypes to high-yielding Mediterranean conditions

Nine wheat genotypes, bred for the high-input agronomical conditions of Henan Province (China), were tested under the high-yielding Mediterranean conditions of Spain. Two cultivars widely grown in the zone were included as controls. Crop growth and leaf chlorophyll (Chl) content, leaf stomatal conductance ( g s ) and canopy temperature (CT) were measured during the crop cycle and stable carbon (C), oxygen (O) and nitrogen (N) isotope compositions ( δ 13 C, δ 18 O and δ 15 N) were analysed on different plant parts. The lower yield of the Chinese genotypes compared with the controls was due to fewer grains/unit area, associated with lower tillering and a plant height clearly below the optimal range. Moreover, Chinese wheat exhibited a lower spike fertility index than the controls, and this was associated with a less compact spike structure. The physiological characteristics that were related to better performance under high-yielding Mediterranean conditions consisted of a higher green aerial biomass, particularly during the reproductive stage, together with more favourable water conditions (higher g s and lower CT and δ 13 C), the capacity to take up water during grain fill (higher δ 18 O) and a more efficient uptake (lower δ 15 N) and utilization (lower leaf N and Chl content) of N fertilizer. It is concluded that Chinese genotypes exhibited a low acclimation capacity to the moderate stress typical of the high-yielding Mediterranean conditions.