Date of this Version
Inconsistency of wheat end-use quality has long been a problem for the milling and baking industries, which require high levels of uniformity for modern, high speed, processing. Extensive research was conducted to characterise genetic, environmental, and biochemical factors that contribute to variation in wheat quality. Samples from 17 locations of trials with 30 cultivars grown over two years were evaluated for grain quality, milling yield, mixograph parameters and baking properties. Protein quality and composition of flour samples were determined by SDS sedimentation and size-exclusion chromatography. Test sites were monitored for soil fertility, and meteorological data was collected hourly during grain fill. Additional grain samples and data were collected from six cultivars grown at 11 locations in 1993. Significant variation in end-use quality was observed among samples; variation was attributed to environmental effects, genotype, and their interactions. For many mixograph and baking parameters, variation attributed to environmental effects was of greater magnitude than for genotype. Increasing levels of low molecular weight (LMW) saline soluble proteins were related to a general decline in dough mixing properties and loaf characteristics. However, correlations of protein components with baking parameters were generally low, suggesting limited predictive value. Hours of high temperature stress (>32 °C) during grain fill were associated with loaf volume and SDS sedimentation volume, although in a curvilinear fashion. Increasing temperature stress initially had a positive influence on loaf volume and protein quality; however, when temperature stress exceeded 90 hours, there was a strong negative influence on baking quality. Variation among cultivars for environmental stability was indicated and cultivar responses to temperature stress varied. Relationships with meteorological data suggest opportunities to predict wheat end-use quality through environmental modelling.