Genotypic variability in the response to elevated CO2 of wheat lines differing in adaptive traits.

Atmospheric CO2 levels have increased from ~280ppm in the pre-industrial era to 391ppm in 2012. High CO2 concentrations stimulate photosynthesis in C3 plants such as wheat, but large variations have been reported in the literature in the response of yield and other traits to elevated CO2 (eCO2). Few studies have investigated genotypic variation within a species to address issues related to breeding for specific adaptation to eCO2. The objective of this study was to determine the response to eCO2 of 20 wheat lines which were chosen for their contrasting expression in tillering propensity, water soluble carbohydrate (WSC) accumulation in the stem, early vigour and transpiration efficiency. Experiments were performed in control environment chambers and in a glasshouse with CO2 levels controlled at either 420ppm (local ambient) or 700ppm (elevated). The results showed no indication of a differential response to eCO2 for any of these lines and adaptive traits were expressed in a consistent manner in ambient and elevated CO2 environments. This implies that for these traits, breeders could expect consistent rankings in the future, assuming these results are validated under field conditions. Additional climate change impacts related to drought and high temperature are also expected to interact with these traits such that genotype rankings may differ from the unstressed condition.