Selection of elite lines in bread wheat (Triticum aestivum L.) using selection indices under drought stress conditions

The most effective approach for genetic improvement of grain yield as a polygenic trait is indirect selection by other traits and simultaneous selection based on the suitable selection indices. The objective of this research was to select the elite lines of bread wheat by selection indices approach. 305 pure lines of bread wheat derived from a cross between Roshan × Falat as well as four check varieties, Roshan, Falat, Mahdavi and Shahpasand, were evaluated as an augmented design at research field of Shahid Bahonar University of Kerman 2013-2014 growing season. In order to apply drought stress, irrigation was cut-off at the emergence stage of the spike and grain yield and other agronomic traits were measured. Among the studied traits, grain weight of main spike, grain weight of single plant, number of grain per plant, 1000- grain weight, number of spike per plant, main spike weight, flag leaf length, spike length and plant weight showed highly genetic correlations with grain yield. Direct and correlated response to selections for grain yield for these traits were calculated. The results indicated that number of spike per plant and number of grain per plant had the highest efficiency for indirect selection. The different selection indices constructed by these traits had the high genetic correlation with grain yield. Moreover, relative efficiency of selection and expected gain of selection index using the Smith-Hazel index was higher than the Pesek-Baker index. Therefore, using the optimum index can be effective in breeding programs of wheat to improve grain yield under drought stress. Finally, 30 elite lines were selected based on each selection index and from their comparison, seven superior and promising lines were identified for further evaluations and introduction to farmers.