Variation in Yield Responses to Elevated CO₂ and a Brief High Temperature Treatment in Quinoa

Intraspecific variation in crop responses to global climate change conditions would provide opportunities to adapt crops to future climates. These experiments explored intraspecific variation in response to elevated CO₂ and to high temperature during anthesis in Chenopodium quinoa Wild. Three cultivars of quinoa were grown to maturity at 400 ("ambient") and 600 ("elevated") μmol·mol^-1 CO₂ concentrations at 20/14 °C day/night ("control") temperatures, with or without exposure to day/night temperatures of 35/29 °C ("high" temperatures) for seven days during anthesis. At control temperatures, the elevated CO₂ concentration increased the total aboveground dry mass at maturity similarly in all cultivars, but by only about 10%. A large down-regulation of photosynthesis at elevated CO₂ occurred during grain filling. In contrast to shoot mass, the increase in seed dry mass at elevated CO₂ ranged from 12% to 44% among cultivars at the control temperature. At ambient CO₂, the week-long high temperature treatment greatly decreased (0.30 × control) or increased (1.70 × control) seed yield, depending on the cultivar. At elevated CO₂, the high temperature treatment increased seed yield moderately in all cultivars. These quinoa cultivars had a wide range of responses to both elevated CO₂ and to high temperatures during anthesis, and much more variation in harvest index responses to elevated CO₂ than other crops that have been examined.