Stability of carbon isotope discrimination and grain yield in durum wheat

Carbon isotope discrimination (A) has been proposed as an indirect selectio n criterion for transpiration efficiency and grain yield in bread wheat (Tr iticum aestivum L.) and barley (Hordeum vulgare L.), with potential value f or durum wheat (Triticum turgidum convar. durum Desf. MacKey). We evaluated the genetic variation for A, the relationship between A and grain yield, a nd the magnitude of genotype X year (G X Y) interactions in durum wheat. Fi eld experiments were conducted under Mediterranean conditions on 144 durum wheat accessions during three successive years. Grain yield and carbon isot ope discrimination of flag leaves (DeltaF) and kernels (DeltaK) were measur ed. Large genotypic and year variation was observed for DeltaF and AK. Flag leaf A was correlated with grain yield in 2 yr characterized as having gre ater water limitation (r = 0.29 - 0.38, P < 0.001). Conversely, DeltaK and grain yield were significantly correlated in all 3 yr (r = 0.49 - 0.52, P < 0.001). In addition, G X Y interactions were significant for DeltaF, Delta K and grain yield. However, significant correlations (P < 0.001) were noted for DeltaK across years. As a result, DeltaK may serve as a better predict ive criterion for higher grain yield under Mediterranean conditions.