Responses of rice cultivars with different cold tolerance to chilling in booting and flowering stages: An experiment in Northeast China

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 & DEG;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.