In Northeast China, the frequency and intensity of chilling events has been increasing continuously, which places regional rice production at an increasing risk for yield loss.Previous studies have shown that continuous chilling at the tillering, booting and flowering stages could reduce rice grain yield. However, the effects of intermittent chilling at different growth stages on rice yield have rarely been reported. In this study, we conducted a temperature-controlled experiment on rice plants at the tillering, booting and flowering stages, with both continuous and intermittent chilling treatments at two chilling temperatures and four chilling durations. The results showed that rice grain yield was most affected by chilling at the booting stage, followed by chilling at the flowering stage and least affected by chilling at the tillering stage. For per 1 day increase in chilling duration, the continuous (intermittent) chilling treatment at T1 (11°C/12°C/12°C) at the tillering, booting and flowering stages decreased the grain yield per plant by 1.0%, 6.0% and 2.9% (0.9%, 2.7% and 1.6%), respectively. For per 10°C•day increase in cooling degree days, the continuous (intermittent) chilling treatment at the booting stage decreased the grain yield per plant, spikelet fertility, grain number per spike and thousand grain weight by 10.7%, 7.9%, 5.4% and 1.6% (5.6%, 1.5%, 4.4% and 1.2%), respectively. While the continuous (intermittent) chilling treatment at the flowering stage decreased the grain yield per plant and spikelet fertility by 4.9% and 3.9% (2.8% and 3.2%), respectively. Our study is complementary to the current knowledge gap concerning the mechanism of chilling-induced yield losses for rice. In particular, the results of this study could be used to (a) modify the chilling effects algorithms in rice models to improve the simulation accuracy in rice yields and (b) target the genetic features to breed new rice varieties with greater cold tolerance.
Climate change has led to an increasing trend in the intensity of global extreme weather events, including chilling. Breeding cultivars with high cold tolerance could be an important pathway to mitigate the negative effects of climate change. For rice, few studies have been focusing on the responses of different cold‐tolerance cultivars on chilling stress. In this study, we selected four japonica rice cultivars and conducted a chilling treatment experiment (with three chilling temperatures and three chilling durations) at the booting and flowering stages in 2020 and 2021 in Northeast China. The results showed that chilling treatment at the booting stage affected the biomass allocation and yield traits more than the chilling treatment at the flowering stage did. Overall, the chilling treatment affected the cold‐sensitive cultivars more than the cold‐tolerant cultivars. Among all the study yield traits, chilling treatment affected spikelet fertility the most, followed by the number of grains per panicle. For every 10°C day increase in CDD at the booting (flowering) stage, the grain yield per plant and spikelet fertility decreased by 4.8–12.8% and 3.6–10.8% (2.1–5.3% and 2.2–4.9%), respectively. Even with the intense chilling treatment, the cold‐tolerant cultivars had relatively high number of effective spikes per plant, grain weight, and stable spikelet fertility, hence they maintained relatively high grain yield. Therefore, it is important to factor in the cold tolerance of the cultivars when assessing the chilling effects on biomass allocation and yield traits for rice. In order to combat the negative effects of extremely low temperature at the reproductive stage on rice grain yield, the future breeding technology could focus on improving the spikelet fertility, grain filling size, and number of spikes per plant.
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