Comparative performance of the stable isotope signatures of carbon, nitrogen and oxygen in assessing early vigour and grain yield in durum wheat

The present paper studied the performance of the stable isotope signatures of carbon (delta C-13), nitrogen (delta N-15) and oxygen (delta O-18) in plants when used to assess early vigour and grain yield (GY) in durum wheat growing under mild and moderate Mediterranean stress conditions. A collection of 114 recombinant inbred lines was grown under rainfed (RF) and supplementary irrigation (IR) conditions. Broad sense heritabilities (H (2)) for GY and harvest index (HI) were higher under RF conditions than under IR. Broad sense heritabilities for delta C-13 were always above 0 center dot 60, regardless of the plant part studied, with similar values for IR and RF trials. Some of the largest genetic correlations with GY were those shown by the delta C-13 content of the flag leaf blade and mature grains. Under both water treatments, mature grains showed the highest negative correlations between delta C-13 and GY across genotypes. Flag leaf delta C-13 was negatively correlated with GY only under RF conditions. The delta C-13 in seedlings was negatively correlated, under IR conditions only, with GY but also with early vigour. The sources of variation in early vigour were studied by stepwise analysis using the stable isotope signatures measured in seedlings. The delta C-13 was able to explain almost 0 center dot 20 of this variation under RF, but up to 0 center dot 30 under IR. In addition, nitrogen concentration in seedlings accounted for another 0 center dot 05 of variation, increasing the amount explained to 0 center dot 35. The sources of variation in GY were also studied through stable isotope signatures and biomass of different plant parts: delta C-13 was always the first parameter to appear in the models for both water conditions, explaining c. 0 center dot 20 of the variation. The second parameter (delta N-15 or N concentration of grain, or biomass at maturity) depended on the water conditions and the plant tissue being analysed. Oxygen isotope composition (delta O-18) was only able to explain a small amount of the variation in GY. In this regard, despite the known and previously described value of delta C-13 as a tool in breeding, delta N-15 is confirmed as an additional tool in the present study. Oxygen isotope composition does not seem to offer any potential, at least under the conditions of the present study.