Evaluation of Freezing Hardiness in Winter Wheat1

Freezing hardiness was evaluated for several winter wheat (Triticum aestivumL.) cultivars and eight selections under controlled freezing conditions. High and low intensity freezing was achieved by decreasing the temperature slowly in hardened wheat crowns containing high and low amounts of water respectively. Freezing hardiness was assessed in terms of lower peripheral crown meristem (root) regrowth on a 0 (dead) to 5 (undamaged) scale. The standard deviation for the freezing test was approximately one meristem rating unit when the number of pots/replication were less than four. Standard deviation increased when the number of pots/replication increased. Different genotypes were easily differentiated when freezing hardiness was evaluated in terms of meristem rating and each genotype replicated 50 times. Many tests were required over a wide range of test temperatures to obtain satisfactory LD50values. Significant interaction in freezing hardiness evaluated either as meristem ratings or as percent survival was found between eight winter wheat selections and freezing condition, but not between 14 wheat cultivars and freezing condition.