Rising winter temperatures and increasing seasonal variability particularly during autumn and spring have contributed to the enhanced survival and proliferation of cold-tolerant weeds such as wild barley and feral rye in wheat fields. These resilient weeds compete aggressively with winter wheat and exhibit high adaptability to fluctuating environmental conditions. Objective: This study aimed to evaluate the freezing tolerance of wheat, wild barley, and feral rye by assessing survival rates, electrolyte leakage, regrowth characteristics, and the maximum photochemical efficiency of photosystem II (Fv’/Fm’). Methods: Plants were exposed to freezing temperatures (0, -3, -6, -9, -12, -15 and -18o C) in tillering stage and their tolerance was measured by determining the temperature at which 50% electrolyte leakage occurred in leaves (T EL50), the lethal temperature for 50% survival (LT50su ), seedlings dry matter and Fv’/Fm’ at -18°C Results: Feral rye exhibited the lowest T EL50 (−16°C),while wild barley showed the highest (−12°C). Wild barley also had thehighest LT50su (−12.6°C), whereas feral rye had the lowest (−15.4°C). At−15°C, the reduction in dry matter for feral rye and wild barley was 33% and 84%, respectively. At −18°C, Fv’/Fm’ decreased by 65%, 70%, 76%, and 39% for wheat cultivars (Pishgam,Ghezel Khoushe), wild barley, and feral rye, respectively. Conclusions: Rising winter temperatures may diminish wheat’s capacity to withstand freezing stress, while more resilient species, such as wild barley and feral rye, may thrive. This shift could result in heightened competition and potential invasions in wheat fields due their natural adaptation to milder freezing conditions.

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