Unveiling the impact of heat stress on seed biochemical composition of major cereal crops: Implications for crop resilience and nutritional value

The predicted rise in global surface and air temperatures, and resulting heat episodes, is a significant challenge for sustaining crop yield and quality in the coming decades. Exposure to heat stress during reproductive and grain-filling stages of crops disrupts source-sink activities and induces undesirable biochemical changes in seeds. While the adverse effects of heat stress on crop production are well-known, the compositional changes in seeds due to heat stress have not received equal attention. Research on the effects of heat stress on seed quality attributes is crucial, as many quality traits that are associated with plant thermotolerance and display good heritability could be exploited to devise breeding strategies to improve crop thermotolerance. Mitigating the negative consequences of heat stress on crop quality via conventional breeding methods or contemporary molecular approaches presents a formidable challenge due to the location and genotype-specific crop responses. Furthermore, the research efforts are impeded by inadequate understanding of the interactions between genotypes and environmental factors. This review explores heat stress mediated alterations in source-sink activities and associated physio-biochemical processes of crops. It presents a comprehensive description of the impact of heat stress on seed quality attributes, including seed carbohydrates, proteins, oils, phytochemicals, vitamins, and dietary fibers, with more emphasis on agronomically important cereal crops like wheat, rice, and maize. Based on the literature review, we conclude by outlining existing research gaps, challenges, and research needs to lessen the negative effects of heat stress on seed quality attributes of nutritional importance.