Mechanisms underpinning cold tolerance in indica hybrid rice: Insights for northern adaptation

Cold tolerance is essential for rice cultivation in northern regions, where low temperatures limit yield potential. This study explores the cold tolerance mechanisms in Liyouyuchi (LYYC), an indica hybrid rice developed by crossing Ruifeng S with R1053, LYYC demonstrated superior cold tolerance, outperforming local varieties with a 16.5 % yield increase in Harbin and a yield of 12.35 t/ha in Jilin in 2023. Under cold stress, LYYC exhibited a lower levels of reactive oxygen species (ROS) accumulation and significantly higher survival rate compared to its parental lines. Genetic analysis identifies several key loci associated with cold tolerance in LYYC, including beneficial allelic variants in GSTZ2, COG1, qCTB7 and Ctb1. Notably, GSTZ2 and Ctb1 exhibited high parent heterosis, while qCTB7 displayed extreme parent heterosis under cold stress, with expression levels significantly higher than both the paternal and maternal lines. The favorable allelic variations in these genes position LYYC as a promising resource for breeding cold-resistant rice varieties. These findings provide valuable insights into the genetic mechanisms of cold tolerance, contributing to the development of rice cultivars better adapted to northern climates and cold-induced stress.