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

Authors: Rohila, Jai; SU, QIONG - Clemson University; KARTHIKEYAN, R - Clemson University

Submitted to: AoB Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2026
Publication Date: 4/15/2026
Citation: Rohila, J.S., Su, Q., Karthikeyan, R. 2026. Understanding effects of heat stress on rice yield and grain quality component traits in rice. AoB Plants. https://doi.org/10.1093/aobpla/plag019.
DOI: https://doi.org/10.1093/aobpla/plag019

Interpretive Summary: Higher temperature during cropping season is detrimental for rice yield and quality. Most studies are either conducted in controlled environments or short-term field experiments, with few studies assessing these effects over whole cropping season in field settings and using multiple varieties. In this study, 36 rice varieties were monitored for high daytime as well as nighttime temperature over the full cropping season in 2016, which was one of the hottest cropping seasons in the past decade. The results revealed that grain yield was more sensitive trait compared with the grain quality trait under heat stress. Flowering contributed the most followed by grain filling stage in yield loss. Grain yield was decreased by 19.4% with a 2-3°C increase in high nighttime temperature (HNT), which approximates an 8% reduction per 1°C increase in mean nighttime temperature. Floret sterility was the main yield component contributing the reduction in grain yield. Among the grain dimension traits, such as grain length, grain width, and grain thickness, grain width was found most sensitive trait under HNT. Several rice genotypes such as Norin 20, ZAO 402, and Geumobyeo were tolerated a small increase in HNT. These findings suggest that optimizing planting dates can be an adaptive strategy to mitigate heat stress under warming cropping seasons.

Technical Abstract: High nighttime temperatures (HNT) negatively impact rice yield and quality, posing a severe threat to global food security. Currently, comparative responses of different varieties to HNT, especially with a small increase (2-3') during various rice growth and developmental stages, are largely unknown. We conducted a field trial of 36 selected rice varieties at two different planting dates in the 2016 growing season in Arkansas, United States. The 36 varieties, including heat-tolerant and susceptible genotypes, were classified into early, medium, and late-maturing types based on heading date and nighttime heat degree days (HDD), was used as an indicator to calculate accumulative HNT heat stress during specific plant stages. We observed a 19.4% decrease in grain yield with a 2-3°C increase in HNT during the flowering and grain filling stages, approximating an 8% reduction per 1°C increase in mean nighttime temperature. Increased floret sterility mainly accounted for the reduction in yield. Early maturing varieties responded as the most tolerant types under the conditions, with decreased floret sterility (P<0.05). Overall, a small increase in HNT showed comparatively little impacts on grain quality traits e.g., a significant decrease in grain width (P<0.05). The differences in response to HNT were significant across varieties indicating availability of genetic variation for heat stress tolerance. We further evaluated the impacts of cumulative nighttime heat stress using HDD-nighttime with a threshold of 21.1', and similar results for the genetic variability were obtained. Norin 20, ZAO 402, and Geumobyeo were identified as potential genotypes to explore quantitative trait loci and superior alleles for better yield and grain quality under HNT. As demonstrated in this study, optimizing planting dates can be an adaptive strategy to mitigate heat stress under warming cropping seasons. The study results also highlight the resilience of early-maturing rice varieties to HNT.