Early or late? The role of genotype phenology in determining wheat response to drought under future high atmospheric CO 2 levels

The combination of a future rise in atmospheric carbon dioxide concentration ([CO ]) and drought will significantly impact wheat production and quality. Genotype phenology is likely to play an essential role in such an effect. Yet, its response to elevated [CO ] and drought has not been studied before. Here we conducted a temperature-controlled glasshouse [CO ] enrichment experiment in which two wheat cultivars with differing maturity timings and life cycle lengths were grown under ambient (aCO approximately 400 μmol mol ) and elevated (eCO approximately 550 μmol mol ) [CO ]. The two cultivars, bred under dry and warm Mediterranean conditions, were well-watered or exposed to drought at 40% pot holding capacity. We aimed to explore water × [CO ] × genotype interaction in terms of phenology, physiology, and agronomic trait response. Our results show that eCO had a significant effect on plants grown under drought. eCO boosted the booting stage of the late-maturing genotype (cv. Ruta), thereby prolonging its booting-to-anthesis period by approximately 3 days (p