Abstract:In this study, 307 accessions of rice (Oryza sativa L.) landraces from different altitude ecological regions in Yunnan Province were used as experimental materials to evaluate the cold tolerance in four growth stages, including the germination stage, the sprout stage, the seedling stage, the booting and flowering stage. The results showed that the cold tolerance in different growth stages for Yunnan rice landraces was significantly or extremely significantly positively correlated with the altitude of the ecological region where they were distributed. In other words, the cold tolerance of Yunnan rice landraces was closely related to the altitude of the ecological region from where they were derived. The cold tolerance in different growth stages for rice landraces distributed in high-altitude ecological regions was significantly stronger than that of rice landraces distributed in low-altitude ecological regions. There was a significant or extremely significant positive correlation among the degrees of cold tolerance in different growth stages, indicating that cold tolerance in each growth stage can be used as indirect indicators for cold tolerance evaluation. Through the identification and evaluation of cold tolerance in four growth stages were screened out 20 landraces (including Lengshuigu, Cizhonghuanggu, Jiegunuo, and Longchuannuo) with grade 1 cold tolerance in germination stage and seedling stage, 9 landraces (including Xiaoheigu, Qitougu, and Yunnangu) with grade 1 cold tolerance in germination stage and booting and flowering stage; 18 landraces (including Bayuenuo, Landigu, and Aolenggu) with grade 1 cold tolerance in seedling stage and booting and flowering stage, and the landrace Aijiaoxi with grade 1 cold tolerance in germination stage, seedling stage, and booting and flowering stage. These excellent germplasms with very strong cold tolerance are of great value and could be used for breeding improvement and new gene discovery for cold tolerance in multiple growth periods.