Managing dryland wheat to produce high-quality grain

The properties of individual grain weight, protein concentration and protein composition contribute to grain quality of wheat. They are known to be affected by genetics, environment and crop management. This paper reports these properties in two dryland field experiments comparing cultivars with similar yield but with contrasting grain weight and number. A large-seeded cultivar, Baviacora, and a small-seeded cultivar, H45, were managed with different nitrogen (N) fertilizer applications and grown in seasons with different rainfall. The aim is to suggest strategies to produce wheat grain of consistently high quality for specified markets, with either pre-harvest or post-harvest management. Individual grain weight and protein concentration varied throughout the spikes of the cultivars and responded to crop management and environment. Protein concentration within a spike was closely correlated with individual grain weight, increasing by 0.05 ± 0.006% per mg of additional grain weight, independent of cultivar or position of grains on the spike. Grain protein composition was related to protein concentration of individual grains but was not as sensitive to individual grain weight. Larger grains were associated with less glutenin per unit of protein, partly offsetting the increase in protein concentration with grain weight. Unextracted polymeric protein (%UPP) was unrelated to grain weight but was negatively related to grain protein concentration in Baviacora. If found to be general, the within-spike relationships between individual grain weight, and the concentrations of grain protein, glutenin and %UPP offer promise for improving grain segregation and post-harvest processing to produce grain of closely defined quality from an unprocessed harvest sample.