Study of Cold Tolerance in some Facultative and Winter Bread Wheat Genotypes in Field Conditions in Maragheh

Winter cold is one of the most important environmental constraints that limits wheat growth, production and yield in many areas in Iran. Thus, selection for cold hardy cultivars could be a vital strategy to avoid winter cold damages and increase yield in cold affected areas. To screen genotypes for cold tolerance two series of crown freezing tests at different periods of winter season were performed in a randomized complete block design with three replications and 20 cultivars at Maragheh Dryland Agricultural Research Station during 2005. Genotypes at two stages of tillering were exposed to different freezing temperatures (ranged from -5 to -23) and their LT50’s were evaluated. In order to evaluate the effect of crown freezing time on cold tolerance a split plot analysis in time was used. Results revealed that genotypes No. 1, 3 and 15 with LT50 of -13˚c were the most cold tolerant and No. 4 with LT50 of -9.33˚c was the least cold tolerant. It was also found that genotypes during the first time of sampling were more tolerant than the second sampling time.