Genotypic response of wheat under semi-arid conditions showed no specific responsive traits when grown under elevated CO<sub>2</sub> MaphosaLancelot FitzgeraldGlenn J. PanozzoJoe PartingtonDebra WalkerCassandra KantSurya 2019 <p>Atmospheric carbon dioxide (CO<sub>2</sub>) is predicted to reach 550 µmol mol<sup>−1</sup> by 2050, increasing from the current ~410 µmol mol<sup>−1</sup> concentration, and this will have an impact on wheat production and grain quality. Genetic differences in response to future CO<sub>2</sub> levels, which might be exploited for higher yield and sustainable grain quality, were investigated. Twelve diverse genotypes (11 wheat lines and 1 triticale cultivar) were grown in the Australian Grains Free-Air CO<sub>2</sub> Enrichment facility under ambient CO<sub>2</sub> (~400 µmol mol<sup>−1</sup>) and elevated CO<sub>2</sub> (eCO<sub>2</sub>) concentrations (550 µmol mol<sup>−1</sup>) in 2014 and 2015 to test for different responses to CO<sub>2</sub>. Genotype response to eCO<sub>2</sub> for the parameters measured showed strong linear relationships. eCO<sub>2</sub> increased plant height (11%), aboveground biomass (31%) and grain yield (32%) as means across all genotypes. Yield response to eCO<sub>2</sub> was driven by increases in spike number and weight. The increase in CO<sub>2</sub> caused a mean 10% decrease in grain nitrogen content and increased grain weight by 7%. Measures of bread dough quality decreased due to eCO<sub>2</sub>. Genotypes with large yield response did not show larger than mean reductions in grain %N. The apparent near-universal decline in grain %N under eCO<sub>2</sub> might be compensated for by selection of genotypes that are highly responsive to increasing yields but resist dramatic declines in grain %N. Selection for responsiveness to eCO<sub>2</sub> for yield and grain %N are likely to involve a range of co-related characteristics that balance sink and source relationships.</p>