Response of wheat grain quality to low temperature during jointing and booting stages-On the importance of considering canopy temperature

Maintaining grain quality under climate change is critical for human nutrition, end-use functional properties and the commodity value. Climate change has resulted in a continuous increase in the frequency, intensity, and duration of extreme low-temperature events, which have affected both the yield and quality of wheat production. To better understand the effects of low temperature on wheat grain quality two-year temperature-controlled experiments were conducted in phytotrons with two different cold-sensitive winter wheat cultivars at four daily maximum/minimum temperature levels and three temperature durations-2, 4 and 6 days-at both jointing and booting stages. In general, low temperature had a positive effect on the protein concentrations and processing quality of wheat but a negative effect on the starch concentrations and appearance quality. Compared with the low temperature duration, low temperature level had a more significant effect on the wheat grain quality, and wheat grain quality was more sensitive to low temperature during the booting than the jointing stage. In addition, significant linear relationships were observed between most of the grain quality indices and cold degree days (CDD) at both stages, which indicated that CDD could be used to quantify the effect of low temperature on crop grain quality well. Furthermore, a comparison of the relationships between the grain quality indices and CDDa (air temperature-based cold degree days) and CDDc (canopy temperature-based cold degree days) indicated stronger correlations between CDDc and nutritional quality. In addition, a relatively stronger positive relationship between CDDa and the processing quality and a negative relationship between CDDc and the appearance quality were observed in the low temperature environment. These results could assist in high quality wheat breeding under future climate conditions.