RESUMO
⢠Accurate phenotyping remains a bottleneck in breeding for salinity and drought resistance. Here the combined use of stable isotope compositions of carbon (δ¹³C), oxygen (δ¹8O) and nitrogen (δ¹5N) in dry matter is aimed at assessing genotypic responses of durum wheat under different combinations of these stresses. ⢠Two tolerant and two susceptible genotypes to salinity were grown under five combinations of salinity and irrigation regimes. Plant biomass, δ¹³C, δ¹8O and δ¹5N, gas-exchange parameters, ion and N concentrations, and nitrate reductase (NR) and glutamine synthetase (GS) activities were measured. ⢠Stresses significantly affected all traits studied. However, only δ¹³C, δ¹8O, δ¹5N, GS and NR activities, and N concentration allowed for clear differentiation between tolerant and susceptible genotypes. Further, a conceptual model explaining differences in biomass based on such traits was developed for each growing condition. ⢠Differences in acclimation responses among durum wheat genotypes under different stress treatments were associated with δ¹³C. However, except for the most severe stress, δ¹³C did not have a direct (negative) relationship to biomass, being mediated through factors affecting δ¹8O or N metabolism. Based upon these results, the key role of N metabolism in durum wheat adaptation to salinity and water stress is highlighted.