Maize Genomics and Genetics 2025, Vol.16, No.3, 129-138 http://cropscipublisher.com/index.php/mgg 133 4.3 Physiological and biochemical markers of reduced yield Physiological and biochemical markers, such as pollen viability, stigma receptivity, and chlorophyll content, can effectively indicate the specific reasons for the decrease in maize yield under high temperature stress. Phenotypic traits such as leaf wilting, tassel sterility, and prolonged flowering-silking interval (ASI) caused by high temperature reduce grain yield, while pollen shedding time and fruiting rate are positively correlated with yield (Alam et al., 2017). High temperature stress interferes with metabolic pathways and dysregulates genes related to starch, lipid, and energy biosynthesis, resulting in reduced starch content, reduced enzyme activity, and reduced pollen germination, leading to sterility (Begcy et al., 2019). The above research results will accelerate the process of developing heat-tolerant maize genotypes (Figure 2) (Djalović et al., 2023). Figure 2 An overview of the impact of heat stress at different developmental stages of maize, impairing maize growth, production, and quality. The reproductive and grain filling period are the most susceptible stages in maize under heat stress. The red colored arrows depict the adverse effect of heat stress and the thickness of those arrows shows the degree of impact on these stages (Adopted from Djalović et al., 2023) 5 Heat Tolerance Genes and Regulatory Mechanisms in Maize 5.1 Identification of heat-responsive genes and QTLs Identification of heat-responsive genes and quantitative trait loci (QTLs) can help analyze and improve heat tolerance in maize, and this method can be used to select heat tolerance at the seedling stage. Transcriptome analysis revealed a large number of differentially expressed genes (DEGs) under high temperature stress. For
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