Stage-Specific Effects of Climatic Variation on Rice Yield and Nitrogen Use Efficiency for Identifying Adaptive Genotypes Based on Variable Selection Method

Extreme weather variability across different climatic regions severely threatens rice yield and nitrogen use efficiency (NUE). To clarify the response of rice traits to climatic factors and optimize adaptive strategies, this study conducted field experiments in Nanjing (subtropical monsoon climate, 2022–2024) and Sanya (tropical marine climate, 2024). Nine rice genotypes covering indica, japonica, and hybrid genetic backgrounds were used, and the least absolute shrinkage and selection operator (LASSO) regression model was applied to identify the key drivers among climatic factors (air temperature, solar radiation, rainfall) and nitrogen application rates. Results showed growth stage-specific responses of rice to climatic stress: high-temperature stress during the flowering stage and low-temperature stress during the filling stage were key yield-limiting factors, while rainfall during the seedling stage and solar radiation during the tillering stage positively promoted yield and NUE. Nitrogen metabolic enzyme activities during the filling stage were the core physiological link connecting environmental stress and yield (R2 = 0.776–0.795). Furthermore, three genotypes (YZ2, IR30, and YZ3) were observed to show more positive associations with yield and NUE. This study clarifies the differential associative effects of climatic factors in tested environments and seasons, providing theoretical support and genetic resources for rice adaptive improvement under diverse climatic conditions.