Adaptive Morphological Responses of Cold Acclimated Wheat Cultivars to Freezing Stress

Abstract

Freezing stress causes irreversible damage to many plants worldwide. As sessile organisms, plants cannot escape stress and must adapt to survive. In freezing-prone regions, successful crop establishment depends on adequate cold hardiness. Climate projections indicate more frequent freezing events in early autumn and late spring, when plants are least prepared. Wheat, a major cereal crop, is affected by freezing temperature in some regions of the world. It possesses a unique cold acclimation (CA) ability, enhancing its freezing tolerance and survival. Selecting cultivars with strong CA capacity is crucial for enduring prolonged freezing conditions. This study examined the effects of CA on growth, freezing survival, and post-freezing recovery in two winter wheat cultivars (Yumechikara and Norin-61) and one spring cultivar (Haruyokoi). Plants were grown in vermiculite-perlite mix maintaining 20 °C for non-acclimated and 4 °C for CA. For freezing stress, a low-temperature programmable incubator was used. Growth analysis revealed a trade-off between vegetative growth and freezing tolerance, with Yumechikara exhibiting the highest freezing survival (over 90%) but reduced growth (14.28 cm) at CA28 days. In contrast, Haruyokoi and Norin-61 showed vigorous growth (17.85 cm and 17.46 cm respectively) but lower post-freezing recovery. Overall, our findings indicate that winter cultivars achieve greater freezing tolerance than spring cultivars by reducing vegetative growth. This demonstrates an inverse relationship between growth and freezing tolerance in the two cultivar types, clearly highlighting a trade‑off. These outcomes also highlight the importance of selecting wheat cultivars with enhanced freezing tolerance and recovery potential to ensure stable yield and productivity in cold-prone regions.