Relation between some agronomic characteristics and grain yield in the advanced wheat genotypes

Abiotic Stresses is one of the most important threatening factors for the production of wheat in cold dryland regions. In order to study some agronomic traits and cold tolerance in rain fed wheat، 20 advanced bread wheat genotypes were evaluated in Azna (regarding agronomic characteristics) and Maragheh for freezing test (LT50) Experimental Stations in 2005-06 cropping seasons. The experimental design was randomized complete block design (RCBD) with three replications. Analysis of variance showed significant difference among the genotypes in most of the traits in Azna region. Freezing test (LT50) study showed that different resistant level of cold tolerant in different date of seedling stages in wheat genotypes and highest cold tolerance related to after hardiness''s with LT50 = -17oC. Based on results Lines with highest grain yield under Azna dryland condition had more cold tolerance. Grain yield showed positive and significant coefficient with spike weight، 1000 kernel weight، biological yield، harvest index and straw yield. The pathanalysisshowed that1000 kernel weight (r= 0. 52**) andharvest index (r= 0. 48**) had highest positive and direct effects on grain yield. Based on results 1000 kernel weight، seed number in spike and harvest index were positive important traits to select of high yield potential lines under drought and cold conditions. Overall suitable genotype for cold and drought area such as Azna need to have more cold tolerance and adapted traits such as TKW، HI and seed per spike for high grain yield production.