Lodging is being increasingly recognized as a critical concern among crop breeders worldwide as it causes a significant reduction in the grain yield and quality of multiple cereal crops. The lodging index is frequently used for evaluating the lodging resistance of rice (Oryza sativa L.) crops. However, the application of lodging index for comparing lodging susceptibility between different rice cultivars is inadequate under certain special conditions. This study was aimed to identify optimized parameters that would evaluate the lodging susceptibility and could then be used along with the lodging index for further assessing the lodging resistance. A total of 32 representative rice accessions from different countries were grown at two different locations on three different sowing dates over a period of 3 yr. The analysis of the lodging index of the different rice cultivars revealed the lodging index value of 200 as the critical threshold value of the evaluated rice accessions. Subsequently, an optimized parameter from the lodging index was proposed. This parameter could be interpreted as the magnitude of the external force that the basal second internode could withstand. A comparison of the optimized parameter values of different rice accessions revealed a previously unknown lodging‐resistant variety R379. The application of the optimized parameter would enable an accurate determination and comparison of the lodging resistance among different rice cultivars, thereby contributing to the effective selection of lodging‐resistant cultivars in rice breeding programs.

Much attention has shifted to the effects of temperature and solar radiation on rice production and grain quality due to global climate change. Meanwhile, lodging is a major cause of rice yield and quality losses. However, responses of the lodging resistance of rice to temperature and solar radiation are still unclear. To decipher the mechanisms through which the lodging resistance might be affected by temperature and solar radiation, 32 rice cultivars with different lodging resistance were grown at two eco-sites on three sowing dates over a period of three years. Based on the field observation, 12 indica rice cultivars which did not lodge were selected for analysis. Significant differences were found in the lodging resistance of the indica rice cultivars at different temperature and solar radiation treatments. The results showed that temperature was the main factor that affected the lodging resistance of indica rice cultivars under the conditions of this study. With the increased average daily temperature, the lodging resistance decreased rapidly, primarily due to the significant reduction in physical strength of the culm, which was attributed to the longer and thinner basal second internode. Among the 12 indica rice cultivars, the lodging-moderate cultivar Chuanxiang 29B was most sensitive to temperature, and the lodging-resistant cultivar Jiangan was least responsive to temperature. These results suggested that rice breeders could set the shorter and thicker basal internode as the main selection criteria to cultivate lodging-resistant indica cultivars to ensure a high yield at a higher ambient temperature.