Relationship between Freezing Tolerance and Leaf Growth during Acclimation in Winter Wheat

Winter hardiness is influenced by many environmental factors, and freezing tolerance is among the main ones, rendering the phenotypic selection of winter wheat (Triticum aestivum L.) under field conditions a difficult task due to the irregular occurrence or absence of winter damage in field trials. Plant growth in response to low temperatures during the acclimation period might be used as an indirect approach to assess freezing tolerance. Thirteen winter wheat cultivars were investigated for autumn and spring growth and winter hardiness under field conditions for two growing seasons. Additionally, a precise and non-destructive technique was applied to study leaf growth at a high temporal resolution accompanied by a freezing tolerance test under laboratory and semi-field conditions. The results of the study revealed variations in thermal growth patterns among the 13 winter wheat cultivars. The cultivars with the lower base temperature (T-b) values, in particular 'Lakaja DS' and 'Sedula DS', grew slower and, thus, had a lower response to temperature increases (Slp(LER-T)) than the fast-growing cultivars, such as 'Simano" and 'KWS Ferrum', whose Slp(LER-T) values were stronger and whose T-b values were higher. A correlation analysis of the investigated traits showed a clear association between leaf growth parameters and freezing tolerance, indicating a certain level of genetic adaptation to growth cessation under low temperatures, and which confirmed that these are important factors for explaining the freezing tolerance of different cultivars. The evaluated freezing tolerance (LT30) showed a strong negative correlation (r = -0.82 divided by -0.89, p = 0.01) to winter hardiness scores from the field experiment, supporting the essential contribution of growth rate patterns to winter hardiness. The findings provide novel information for the development of winter-hardy wheat cultivars that are adapted to the future environments.