Tolerance of Different Winter Wheat Cultivars to Prolonged Freezing Injury at their Critical Temperatures

Inconsistent survival during winter due to freezing injury of varying severity is a major impediment to winter wheat ( Triticum aestivum L.) growth and productivity. To evaluate the tolerance of different winter wheat cultivars and different organs of the same cultivar to prolonged freezing injury, 3 yr of controlled freezing experiments were performed with four cultivars under different freezing durations at the cultivars’ corresponding critical temperatures. Experimental plants in plastic pots that have hardened in the field were moved to freezing chambers for controlled freezing treatments during the winter. A highly significant relationship was observed between freezing duration and mortality for each of the different cultivars and organs. For every 1‐d increase in freezing duration at the critical temperature, plant mortality increased by 8.6, 22.3, 11.1, and 9.4% for cultivars Jing411, Nongda211, Zhengmai366, and Yanzhan4110, respectively. Within the same cultivar, tillers (15–32% d −1 ) were less sensitive to freezing duration than younger leaves (25–35% d −1 ) and older leaves (20–55% d −1 ). Spike number was greatly influenced by freezing duration and the resulting death of tillers. For every 1% increase in tiller mortality, spike number per pot declined by 1.3, 2.0, 1.2, and 0.7% for cultivars Jing411, Nongda211, Zhengmai366, and Yanzhan4110, respectively. These findings indicate that reducing tiller death during winter is important for preventing extensive decreases in spike number.