Natural Variations of Spring Wheat Nitrogen and Carbon Assimilation under Different Inorganic Nitrogen Forms and CO2 levels

Wheat ( Triticum aestivum L.) production depends upon nitrogen fertilization and may be threatened by the climate conditions anticipated in the next few decades. The natural variation in the ability of wheat to assimilate carbon and different inorganic nitrogen forms, nitrate (NO ₃ ^- ) and ammonium (NH ₄ ⁺ ), into vegetative growth remains unexplored. Here, we evaluated growth under either NO ₃ ^- or NH ₄ ⁺ as a sole nitrogen source for 875 spring hexaploid wheat accessions that represent the genetic diversity within the global germplasm. These accessions varied over 8-fold in vegetative biomass but grew similarly under moderate levels of either nitrogen form. At high, potentially toxic concentrations of NH ₄ ⁺ , however, they lost approximately 20% of their biomass. We characterized the influence of changing CO ₂ levels in bi-parental Nested Association Mapping populations. Genetic backgrounds determined wheat biomass responses to CO ₂ enrichment and nitrogen form. Genome-Wide Association and linkage mapping identified certain loci as consistently associated with biomass accumulation under different nitrogen forms and CO ₂ levels. These results will assist breeding efforts to develop food crops that are resilient to the world’s climate changes.