Growth Environment and Wheat Quality: the Effect of Heat Stress on Dough Properties and Gluten Proteins

High temperatures (e.g. daily maxima over 35°C occurring during grain filling) have been identified as major source of variation in dough properties in wheat. Such conditions may occur in the wheat-cropping areas of many countries with sufficient frequency for this phenomenon to be a significant marketing factor. The association of heat stress with dough weakening was indicated by analysis of historical data from crop statistics, cultivar trials and field experiments. Glasshouse and growth-cabinet experiments have further validated the conclusions, and have led to the formulation of a molecular mechanism to explain these results. This involves the identification of heat-shock elements upstream of the coding region of certain gliadin proteins, but not for glutenin polypeptides. As a result, gliadin synthesis continues at a greater rate than glutenin synthesis during a period of heat stress. Consequently, the mature grain has a higher ratio of gliadin: glutenin and produces weaker dough. These results now provide a basis for formulating strategies to minimize variations in dough properties due to growing conditions.