Carbon isotope discrimination and mineral composition of three organs in durum wheat genotypes grown under Mediterranean conditions

Carbon isotope discrimination (Δ) has been proposed as a good criterion for transpiration efficiency and grain yield improvement. Its measurement, however, remains very expensive. Ash content (m_a) has been proposed as an alternative criterion for Δ in bread wheat and barley. The aims of this study were (i) to analyse the relationships between Δ and mineral composition in different durum wheat plant parts and (ii) to compare the variation of these traits between landraces and improved varieties from different geographic origins. For this purpose, Δ, m_a, and composition in four minerals (K, Mg, P and Si) were assessed in flag leaves and awns at anthesis, and in mature grains of ten durum wheat genotypes grown under rainfed Mediterranean conditions. The three plant parts differed significantly for the measured traits. Significant correlations were noted between Δ and m_a in the flag leaf and in the grain. Silicon content in flag leaves and potassium content in awns were also positively related to Δ of the considered plant part. The coefficient of correlation between Δ and m_a was generally higher than that observed between individual mineral content and Δ, suggesting that m_a is the better alternative criterion for Δ. In addition, grain yield was related to grain Δ and both m_a and potassium content in awns. Harvest index was correlated with Δ and m_a of grain and flag leaf. These results emphasised that m_a values in flag leaf and grain represent the efficiency of carbon partitioning to the grain. Improved varieties showed higher Δ and m_a values than landraces. Differences between Middle-East and West Mediterranean genotypes for the measured traits were also presented and discussed.