Relationships between flag leaf carbon isotope discrimination and several morpho-physiological traits in durum wheat genotypes under Mediterranean conditions

Relationships between flag leaf carbon isotope discrimination (Δ), water status parameters, residual transpiration (RT) and stomatal density (SD) were examined on a collection of 144 durum wheat accessions. Associations between Δ, grain yield (GY) and harvest index (HI) were also studied. The field trial was conducted under Mediterranean conditions. The crop cycle was characterised by a period of drought from February until maturity. A broad range of values we obtained for Δ (16.5–19.9‰) and other physiological traits. Flag leaf Δ was positively and significantly correlated with both HI and GY. Δ was better correlated with HI than with GY, which suggests that higher Δ values indicate higher efficiency of carbon partitioning to the kernel, leading to higher GY. Δ was found positively related with RT and negatively related with SD. This relationship may indicate a possible SD component of RT due to the association between conductance and SD. Strong positive correlations were found between Δ and water status parameters, suggesting that Δ may provide a good indication of plant water status in durum wheat under rainfed Mediterranean conditions.