Study of Cold Tolerance and some Agronomic Traits in Bread and Durum Wheat Genotypes in Dryland Areas

Low-temperature (LT) is one of the limiting factors causing loss of yield in cereals in cold regions of Iran. Cold tolerance as measured by LT50 was determined for cold acclimated crowns of plants grown in the field at the Maragheh Research Station in 2004 and 2005 crop seasons. A randomized complete block design was set up for 90 bread and durum wheat genotypes in three and four replications under field conditions for cold and yield trials respectively. In general, advanced winter bread wheat genotypes showed intermediate levels of LT tolerance (average LT50=-15.63C). Day to maturity and grain filling duration had positive relation with cold tolerance (r = 0.46** and r = 0.54** respectively). Grain yield showed negative significant correlation with cold tolerance (r = -0.23*). Results indicated that the late maturing genotypes, had more tolerance to cold, but in cold dryland areas selected lines not only should have high yield and good cold tolerance, but also they should have earliness and other good traits for resistance to terminal drought stress. Genotypes No. 15, 17, 23, 30, 41 and 53 had the highest grain yield and high tolerance to cold. Based on results the highest tolerance up take after hardening to cold, and after 1.5 to 2 months of hardening degree of cold tolerance will be decrease.