Osmotic Potential of Winter Wheat Crowns for Comparing Cultivars Varying in Winterhardiness

Cold hardening of winter wheat (Triticum aestivum L.) crowns results in decreased water content, and in increases and changes in solutes. These facts led us to hypothesize that osmotic potential (ΨII) of hardened wheat crowns might be used as a screening technique for winterhardiness. Winter wheat with different levels of winterhardiness, ranked from long‐term trials, were grown in the field. Periodically, during two winters, plants were removed and the ΨII of the crowns determined. Contrast comparisons between two hardy, and two or three less hardy cultivars showed significant differences, at every sampling date with the hardy lines having lower ΨII. During one winter the ΨII of 24 cultivars whose winter‐hardiness had been evaluated over several years in the field was determined on three dates. Linear correlations (r2) between field scores (5 = most winterhardy, 1 = least hardy) and ΨII were highly significant, and varied from 0.75 to 0.83. Based on these data, we suggest that measurement of ΨII of winter wheat crowns following cold acclimation may be a valuable tool in the selection of winterhardy wheat cultivars