Heat Stress and Grain Quality

AbstractCereals are the main source of energy for the majority of world population. The composition and quality of the cereal grains are affected by different types of stresses. High-temperature stress, especially during grain filling, has a severe impact on grain quality mainly due to changes in accumulation and distribution of different macro and micronutrients. The impacts of heat stress during grain filling may vary among different crop species depending on the intensity, duration, and timing of the stress. Exposure to high temperatures during grain filling alters the expression of many genes related to starch biosynthetic pathways, starch transporters, transcription factors, and storage proteins. The activities of the main enzymes involved in starch synthesis are reduced leading to the reduced content of starch, changes in the shape and size of starch granules, alterations in the amylose: amylopectin ratio, and branching patterns. Heat stress, even for a few days during the grain filling period can have a major impact on protein composition. The changes in glutenin: gliadin ratio in wheat flour significantly alter the dough strength. The changes in starch and protein composition lead to the changes in rheological and physicochemical properties of flours which may finally affect the quality of the end products. In this chapter, the effects of heat stress on four major cereals, i.e., wheat, rice, maize, and barley, are discussed separately because of the differences in quality requirements for their utilization in the production of different types of end products.KeywordsHeat stressGrainfilling periodGrain qualityStarchProtein