The increase in atmospheric carbon dioxide (CO2) concentrations is the most certain trend among all climate change predictions. Apart from the role of increasing CO2 in changing global temperature and rainfall patterns, such a large change in one of the main resources for plant growth also have a significant impact on all plants and ecosystems. Any envisaged adaptation of crops and cropping systems to future climates can therefore not neglect the direct and interactive effects of increasing atmospheric CO2 concentrations.
In this project a range of wheat types were grown in the AGFACE facility to identify crop traits that pre-breeders may be able to exploit to produce cultivars better adapted to a high CO2 atmosphere. Wheat types were chosen to represent, and allow researchers to evaluate, traits of current or potential importance to wheat breeders, in particular transpiration efficiency and the capacity to form secondary shoots (tillers).
Results from the study demonstrate that elevated CO2 (eCO2) can increase yields under these environmental conditions by more than 20% and improve leaf level transpiration efficiency of wheat, but at the same time decrease nitrogen and other nutrient concentrations in vegetative biomass, and decrease concentrations of essential micronutrients and protein in grains.
Despite the general increase in leaf level water use efficiency under eCO2, a cultivar selected for improved transpiration efficiency had a yield advantage under eCO2 which was not evident under current CO2. This result suggests that selection for transpiration efficiency under eCO2 will provide an even larger gain than under current atmospheric concentrations, making it an important adaptation strategy.
High tillering varieties of wheat were expected to have increased yields under eCO2, with studies from high rainfall environments showing a positive correlation between tiller numbers and yield. However, AGFACE results show that wheat types with restricted tillering capacity can gain similar yield increases as some freely tillering types if they have sufficient plasticity in other yield components, such as a capacity to increase kernel weights.
The results of this project convinced the Grains Research and Development Corporation to support further in-depth research at AGFACE on wheat traits and on the more commercially relevant aspects of grain quality raised in the current project. The study has also highlighted further research needs towards strategies for improved nutrient use efficiency of crops for eCO2, adapting crop nutrient management eCO2 conditions, adapting current strategies to fortify grain micronutrient content, and adapting strategies to improve crop stress tolerance under consideration of eCO2.
This project was funded by the Australian Government Department of Agriculture, Fisheries and Forestry through its Climate Change Research Program.