Grain quality response to elevated CO₂

Grain quality response to elevated CO₂

Background

For farmers, achieving consistently high grain quality goes hand in hand with high yields. While wheat quality traits are highly heritable, each trait is affected to varying degrees by abiotic factors during plant growth and grain filling.

Elevated carbon dioxide (eCO2) and ambient temperature are known to affect grain chemical composition, which in turn affects baking and milling quality traits.

Project outline

Micronutrients, and protein amount and quality have been measured under eCO2 to assess the impact on human diets. Protein and starch quality are being quantified to determine if there could be changes to Australian markets and wheat classification. These data have also been used to test a predictive model for milling yield. Since grain, bread and noodle quality are altered by varieties and environment, the impact of eCO2 has been tested on multiple wheat varieties under a range of conditions.

Taken together, these analyses will allow the industry to understand changes in bread and noodle quality, human nutrition and wheat quality in terms of the Australian Wheat classification system.

In an additional project component conducted as part of the ‘NFACE’ experiment, researchers are studying whether the changes in grain protein and protein composition can be reversed through nitrogen management. The experiment will investigate three nitrogen management techniques: split nitrogen application, foliar nitrogen application, legume pre-cropping.

Results

Under eCO2, wheat grain protein content was consistently reduced across all varieties and environments and there were complex changes to protein composition. Together these contributed to a reduction in bread loaf volume and malformed loaves. In contrast, there were positive effects on noodle quality, particularly colour stability.

The effects of eCO2 on quality parameters varied across cultivars, providing an opportunity for selection of genotypes that are less affected by changes in protein under eCO2. Simulation modelling of varietal x environment effects is a tool that could complement field-based methods for selecting better adapted wheat traits; however the required parameters are not currently available in most models.

Micronutrient composition in grain was also reduced under eCO2, particularly zinc and iron, and this is a global phenomenon. Along with protein reduction, this could have consequences to millions of people who have limited access to sufficient food. Micronutrient and protein concentration decreases tend to follow yield increases, suggesting a “dilution” effect but not all cultivars follow this trend, highlighting the potential for selection of genotypes that resist this reduction (e.g. biofortification).

In the 2015 NFACE study, there were strong yield and protein responses to different rates of urea nitrogen applied at sowing but the addition of fertiliser in the first year of the experiment did not overcome the protein reductions resulting from eCO2. Preliminary analyses indicate that there were no significant differences in protein levels between the nitrogen management techniques.

Next steps

A second growing season will confirm treatment responses to nitrogen management obtained in 2015. The ongoing study will also focus on variety X rate effects, and assess 'novel' nitrogen treatments to better synchronise nitrogen supply with crop demand.

 

Related resources

Titlesort ascending Excerpt
Joe Panozzo - AGFACE results: Impact of elevated carbon dioxide on grain quality Presented by Joe Panozzo, DEPI, at the AGFACE Crop Science Workshop. 
AGFACE fact sheet (2014) Fact sheet profiling the project Australian Grains Free Air Carbon dioxide Enrichment program.