Relationships between freeze tolerance and plant architecture in winter wheat during tillering stage

Winter freezing injury is a critical factor limiting wheat(Triticum aestivum L.) productivity in northern China. Since freeze tolerance (FT) correlates with seedling growth traits, this study investigated the relationship between FT and plant architecture (PA) in winter wheat at the tillering stage. We evaluated 550 wheat varieties and advanced lines from the Huang and Huai River Valleys Winter Wheat Zone of China. Seedling PA was classified using the International Union for the Protection of New Varieties of Plants (UPOV) standards, while FT was evaluated through two parameters: severity of leaf necrosis (SLN) and mortality rate of shoots (MRS). The results showed that the PA distribution across germplasms approximated a normal distribution. The relationships between SLN and MRS under freezing stress were highly variable across years with differing winter conditions. SLN and MRS-derived FT levels showed a positive correlation within the same growing season but were inconsistent across different years. PA and MRS showed no correlation whereas correlation between seedling PA and SLN varied substantially across years. Due to inadequate cold acclimation in 2022-2023 and heavy snow cover in 2023-2024, there was no significant correlation between FT levels and seedling PA during these periods. A significant negative correlation was observed between PA and SLN during the 2024-2025 season, indicating that more prostrate growth habits were associated with a reduction in leaf necrosis. These results indicate that architectural traits may contribute to FT only within certain environmental contexts. Thus, enhancing freezing tolerance should focus on direct survival tests in various environments, with secondary traits like SLN and PA considered as context-dependent factors.