Abstract
Postflowering heat stress causes the arrest of kernel growth, increasing kernel protein concentration and the relative abundance of γ‐zeins, two biochemical traits contributing to maize (Zea mays L.) hardness. The impact of early and late postflowering heat stress on kernel physical traits related to hardness was studied on field‐grown maize hybrids differing in their prevailing endosperm texture (two hybrids with a vitreous texture, and two others with a floury texture). Kernel texture was softened by heat stress (P < 0.001), as indicated by decreases in traits that are usually positively related to hardness (thousand‐kernel weight [up to 185 g], proportion of large kernels [up to 50–65 percentage points], kernel or bulk density [up to 7 kg hL−1] and milling ratio [up to 1 g g−1]) and increases in those usually negatively related (proportion of the smaller kernels and floater percentage [up to 30 and 75 percentage points, respectively]). Most of these effects were larger (P < 0.01), as heat stress occurred earlier in the grain‐filling period. Kernel physical traits of the genotypes with a predominantly floury texture varied the most (P < 0.05) in response to heat stress. Genotypic and environmental variation effects in most hardness‐related traits could be accounted for by kernel density (r2 = 0.74–0.87) or bulk density (r2 = 0.79–0.93). Sowing date and genotype selections should be considered as crop management practices for reducing or preventing the potential impact of heat stress on maize hardness.
Published Version
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