Abstract

Cold stress is a worldwide abiotic stress in temperate regions that affects plant development and yield of winter wheat (Triticum aestivum L.) cultivars and other winter crops. This study was conducted to evaluate the effect of freezing stress at the early growing season on survival and also the relationship between resistances tofreezing stress at this stage with drought resistance after postanthesis in eight Iranian bread wheat cultivars. An experiment was laid out in a split–plot arranged in a randomized complete blocks design with three replications. Under control treatment among all cultivars, Marvdasht and Chamran cultivars had the lowest grain yield andbiomass; except these two cultivars there were no significant differences between others. Postanthesis water stress caused more reduction in grain yield of Zarin, Phishgam and Marvdasht and biomass of Phishgam and Parsi cultivars, respectively. The lowest and highest LT50 temperatures of crowns at the early growing season were seen in Marvdasht (-4°C) and Pishtaz (-1.13°C) cultivars, respectively. Correlation coefficients of soluble and insoluble sugars concentration between crown survivals under freezing stress were, respectively positive and negative. Grain yield under postanthesis water stress had the highest correlation coefficient (R=-86.2%)with crown survival under freezing stress at the early growing season. Therefore,postanthesis water stress-sensitive cultivars were more resistant to freezing stress at the beginning of growing season after the cold of winter.

Key words: Wheat, cold stress, freezing stress, crown, soluble sugar.