An experimental study on the effects of intermittent chilling at different growth stages on rice yield in Northeast China

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 degrees C/12 degrees C/12 degrees 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 degrees C center dot 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.