Adaptive traits do not mitigate the decline in bread wheat quality under elevated CO2

Abstract

Increased levels of atmospheric CO2 levels (eCO2) have been shown to decrease Grain Protein Concentration (GPC) and alter wheat composition (both protein and carbohydrate components). Lower GPC and altered composition under eCO2 conditions have deleterious impacts on end-product processing, dough rheology and bread loaf volume. To determine if the decline in GPC in wheat under eCO2 could be circumvented, traits hypothesised to improve grain protein were assessed in the Australian Grains Free Air CO2 Enrichment (AGFACE) facility. Wheat genotypes were selected with enhanced nitrogen use efficiency, water use efficiency, root vigour and grain quality, and were exposed to eCO2 (550 μmol mol−1) to determine if grain quality could be retained. Results showed that these trait strategies were not able to prevent the significant decline in GPC or grain quality (P ≤ 0.001). The decline in loaf volume (P ≤ 0.001) was greater under eCO2 across the selected cultivars and environments is likely associated with reduced GPC, changes in gluten protein composition, and significant increases in arabinoxylan content. Larger quantities (increased yield, P > 0.05) of lower quality grain will be produced in the future climates (eCO2), unless crop breeding efforts focus on grain-nitrogen translocation traits so that wheat can retain high quality grain under eCO2.