Grain protein concentration at elevated [CO2] is determined by genotype dependent variations in nitrogen remobilisation and nitrogen utilisation efficiency in wheat.

Predictions for wheat grown under future climate conditions indicate a decline in grain protein concentration accompanied with an increase in yield due to increasing carbon dioxide concentrations. Currently, there is a lack of understanding as to the complete mechanism that governs the response of grain protein concentration (GPC) to elevated carbon dioxide (e[CO2]). We investigated the GPC of 18 wheat genotypes from a doubled haploid wheat population and the two parental genotypes, Kukri and RAC0875. In addition, other nitrogen and biomass related traits were analysed to further elucidate which traits are connected with the decline in GPC. Wheat was grown under ambient and elevated [CO2] in an environmentally controlled glasshouse. Plant nitrogen and biomass accumulation were measured at anthesis and maturity. We found that GPC declined under e[CO2] and that the response of GPC to e[CO2] was negatively correlated with nitrogen utilisation efficiency and harvest index. The extent that total biomass (anthesis), harvest index, photosynthesis, nitrogen utilisation and remobilisation efficiency, total nitrogen remobilisation and post-anthesis nitrogen uptake impacted GPC in response to e[CO2] varied across genotype, suggesting that multiple mechanisms are responsible for GPC decline at e[CO2] and that these mechanisms are effected differentially across genotypes.