Significant decrease in yield under future climate conditions: Stability and production of 138 spring barley accessions

The response in production parameters to projected future levels of temperature, atmospheric carbondioxide ([CO₂]), and ozone ([O₃]) was investigated in 138 spring barley accessions. The comprehensive setof landraces, cultivars, and breeder-lines, were during their entire life cycle exposed to a two-factor treat-ment of combined elevated temperature (+5^◦C day/night) and [CO₂] (700 ppm), as well as single-factortreatments of elevated temperature (+5^◦C day/night), [CO²] (700 ppm), and [O₃] (100–150 ppb). Thecontrol treatment was equivalent to present average South Scandinavian climate (temperature: 19/12^◦C(day/night), [CO₂]: 385 ppm). Overall grain yield was found to decrease 29% in the two-factor treatmentwith concurrent elevation of [CO₂] and temperature, and this response could not be predicted from theresults of treatments with elevated [CO2] and temperature as single factors, where grain yield increased16% and decreased 56%, respectively. Elevated [O₃] was found to decrease grain yield by 15%. Substantialvariation in response to the applied climate treatments was found between the accessions. The resultsrevealed landraces, cultivars, and breeder-lines with phenotypes applicable for breeding towards stableand high yield under future climate conditions. Further, we suggest identifying resources for breedingunder multifactor climate conditions, as single-factor treatments did not accurately forecast the response,when factors were combined.