Identification of Effective Traits on Grain Yield of Bread Wheat Genotypes in Rainfed and Supplementary Irrigation

The development of high yielding cultivars is the main goal of many wheat breeding programs and the realization of it depends on the relationship between grain yield and its components. To investigate the relationship between grain yield and some morphological characteristics and to determine the relative importance of each of them, 25 bread wheat genotypes were evaluated in both rain-fed and supplementary irrigation systems with randomized complete block design with three replications during the farming periods in a farm featuring Mediterranean climate in west of country between 2014 and 2016 (Kermanshah’s Sararud Rain-Fed Agricultural Research Station). Variance Analysis results showed significant differences among lines for all studied traits in both rain-fed and supplementary irrigation. Simple correlation coefficients between traits in both conditions indicated that cell membrane stability, flag leaf length, Awn length, relative water content, thousand grain weight and chlorophyll content, are significantly correlated with the grain yield. Regression analysis showed that peduncle length, relative water content, proline content and chlorophyll content in rainfed and traits such as the relative water content and proline content for the supplementary irrigation condition were introduced into regression model, 0/906 and 0/840 of the total changes related to grain yield, respectively.To determine the direct and indirect effects of traits on yield, path coefficient analysis was done, the highest positive direct effects on grain yield were related to peduncle length, relative water content and chlorophyll content under both mentioned conditions, that showed important characteristics in relation to grain yield. Genotype No.1 (Azar2) for supplementary irrigation conditions and Genotype No. 25 (Rijjaw) for rainfed conditions are superior to the rest of the studied cultivars and lines also can be introduced for cultivation in the climatic conditions of the study area. The physiological characteristics of leaf relative water content, proline content and chlorophyll content as well as morphological traits of peduncle length and flag leaf length are introduced as suitable traits for the improvement of rainfed cultivars.