Understanding the effects of heat stress on yield and grain quality component traits in rice

per °C·day; ∼1.4% per HDD). Grain traits varied among maturity groups, with medium- and late-maturing varieties producing thinner and chalkier grains, while early-maturing varieties largely maintained grain weight. Across traits, variety and maturity group explained most variation, and significant variety × planting date interactions highlighted exploitable genotype-by-environment (G × E) effects on nighttime heat tolerance. Early-maturing varieties, including Norin 20, ZAO 402, and Geumobyeo, demonstrated strong resilience to HNT stress. Planting dates adjustments may, therefore, offer a practical adaptation strategy to mitigate heat stress under warming cropping seasons, although further investigation is needed.