Rice yield and quality in response to daytime and nighttime temperature increases – a meta-analysis perspective

Authors: SU, QIONG - Clemson University; Rohila, Jai; KARTHIKEYAN, RAGHUPATHY - Clemson University; RANGANATHAN, SHYAM - Clemson University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2023
Publication Date: 7/7/2023
Citation: Su, Q., Rohila, J.S., Karthikeyan, R. 2023. Rice yield and quality in response to daytime and nighttime temperature increases – a meta-analysis perspective. Science of the Total Environment. https://doi.org/10.1016/j.scitotenv.2023.165256.
DOI: https://doi.org/10.1016/j.scitotenv.2023.165256

Interpretive Summary: The rice growing areas in the U.S. and several regions of the world are experiencing hotter ambient temperatures during rice cropping season. The high day temperature (HDT) and high night temperature (HNT) affect overall rice well-being, fertility, grain-filling process, and thus eventually lowers grain yield, grain quality, and profitability for rice growers. A lot of studies have been conducted as individual small experiments, but still a clear understanding for a relationship between rice yield and high daytime/nighttime temperatures is lacking. In this meta-analysis paper, we study the daytime/nighttime temperatures as one big data set by compiling data from 1105 experiments for HDT and 841 experiments for HNT from 73 peer-reviewed papers that were selected based on certain criterion such as daytime/nighttime temperatures, yield components and several rice quality traits. The study found that the ideal day/night temperature for rice is 28'/22'. Higher nighttime temperature had higher impact on yield compared to the high daytime temperature, and the yield loss under heat stress was associated with impact on rice quality traits. We found that however, HDT and HNT, both had negative effects on grain yield, but grain yield showed a little more sensitivity to higher nighttime compared with daytime temperatures, decreasing rice yields by about 7% for every 1' increases in nighttime temperature with an assumption of 22' as the optimum night temperature. Also, the yield loss under heat stress was found associated with significant impacts on rice quality traits. One major outcome of this meta-analysis was the development of a new working hypothesis about heat stress tolerance in rice. Based on the results, we proposed that while the highest ambient temperature reading during day and night could be important, total heat degree hours (HDH) during day and night are critically important and their interaction must be considered in future experiments.

Technical Abstract: Increased heat stress during cropping season poses significant challenges to rice production, yet the complex stoichiometry between rice grain yield, quality and high daytime, nighttime temperature remains with gaps in current knowledge. We conducted a meta-analysis using a combined dataset of 1105 experiments for high daytime temperature (HDT) and 841 experiments for high nighttime temperatures (HNT) from peer-reviewed published articles to investigate the effects of high daytime temperature (HDT) and high nighttime temperatures (HNT) on rice yield components (such as panicle number, spikelet number per panicle, percent fertility, grain weight) and quality traits (such as milling yield, chalkiness, amylose and protein contents). We constructed dose-response curves and studied phenotypic plasticity of rice traits in response to HDT and HNT. The results suggest that HNT had a more detrimental impact on rice yield and quality when compared with HDT. The optimum daytime and nighttime temperatures for best rice yield were approximately 28 ' and 22 ', respectively. Grain yield showed a decline by 7% and 6% for each 1 ' increase in HNT and HDT, respectively, when exceeded the optimum temperatures. The seed set rate (percent fertility) was the most sensitive trait to HDT and HNT and accounted for most of the yield losses. Both the HDT and HNT affected grain quality by increasing chalkiness and decreasing head rice percentage, which may affect rice marketability of the rice produced. Additionally, HNT was found to significantly impact nutritional quality (e.g., protein content). The dose-response curve analyses suggest that while the highest ambient temperature reading during day and night could be important, total heat degree hours (HDH) during daytime and nighttime seems to be critical for deciding tolerance or susceptibility of rice germplasm. Further, the findings fill current knowledge gaps on estimations of rice yield losses and possible economic consequences under high temperatures and suggest that rice quality impacts should also be considered for selection and breeding of high-temperature tolerant rice varieties in responses to HDT and HNT.