No abstract

Field and laboratory experiments were carried out to determine the effect of cold stress on fifteen wheat (Triticum aestivum L.) cultivars. Fifteen cultivars including winter cultivars viz., Sayson, Marton, Gaskoghen, C-82-12, C-82-13, facultative cultivars: Alvand, Mahdavi, Zarrin, Marvdasht, Tous and spring cultivars viz., Shiraz, Pishtaz, M-79-7, M-81-13, Kavir were sown at three dates (15 October, 15 November and 15 December) based on complete blocks design with three replications under field conditions. In laboratory experiment the same cultivars were evaluated under cold stress at two and four leaves growth stages. Results showed that there were significant differences among cultivars in grain yield, potassium accumulation, lethal temperature (LT 50 ), ion leakage, chlorophyll content a and b among growing stages, genotypes and interaction between them. Ion leakage was the highest for M-81-13 cultivar (81.12ds m -1 ). C-82-12 and Gaskogen with more than 6.44 % and Sayson with 4.89 % potassium accumulations had the highest and lowest values. Lethal temperature of Gaskogen and Shiraz were -42 and -28°C. Gaskogen was tolerant to cold stress and hadn't high grain yield potential. The highest chlorophyll a and proline content were obtained for Marvdasht and Gaskoghen with 2.51mg.g-1 and 0.34g.g-1 at two leaves growth stage. In contrast the lowest chlorophyll b related to Sayson and C-82-12 with 1.37 and 1.39 mg g-1 , respectively. All cultivars at first planting date had more grain yield than two other planting dates.