Changes in wheat grain quality due to doubling the level of atmosphere CO2

Elevated levels of atmospheric CO2 have been shown to increase grain yield and reduce grain nitrogen concentration. The object of this study was to determine whether elevated CO2 levels would modify other aspects of grain quality relevant to processing, particularly protein and starch quality. Wheat of two genotypes (Hartog and Late Hartog) was grown in the field in controlled-atmosphere tunnels at either the ambient level of CO2 (350 microliters/L) or an elevated level (700 microliters/L). This elevated level of CO2 produced significant increases in grain yield, but decreases in 1,000-kernel weight. Grain grown in the elevated CO2 atmosphere produced poorer dough and decreased loaf volume, farinograph development time, and dough extensibility. These changes were largely attributable to the lower protein content of the grain grown at elevated CO2. There did not appear to be major changes in protein composition or in the functional properties of the protein. Grain produced at elevated CO2 yielded starch with a significantly higher proportion of large (A-type) starch granules but no overall change in amylose-to-amylopectin ratio. These studies indicate that elevated levels of CO2 may result in decreased quality of bread wheats largely due to lowered protein content