Evaluation of some Physiological Traits in Drought Tolerant Lines of Bread Wheat in Rainfed Conditions

Study of physiological traits and the relationship between these traits and grain yield in drought stress conditions can be useful to identify effective physiological traits involving in resistance to drought stress. In order to study these traits، parameters such as gas exchange، water status، flag leaf characteristics، chlorophyll content index، grain yield and thousand grain weight were measured in twenty bread wheat genotypes (18 lines، together with Sardari and Azar 2 cultivars). The experiment was conducted in rainfed condition at Agricultural Research Station of Gheidar، Zanjan، Iran. Mean comparisons showed that line No. 4 and cultivar Azar 2 had the highest grain yield among the genotypes. Genotypes having lower internal CO2 concentration and higher thousand grain weight، produced higher yield. Decrease in photosynthesis was mainly due to non-stomatal limitations، and high grain yield was not related to leaf relative water content. Cluster analysis and principal component analysis based on measured traits classified genotypes into three separate clusters. Based on the overall results of present study، genotypes No. 2، 4، 8، 10، 13، 17، 6 and 18 were superior than the others under rainfed condition.