Construction of some selection procedures for improvement of grain yield in durum wheat

The purpose of this study was to estimate and compare the genetic gain obtained from the Smith-Hazel index model of selection index with direct selection to enhance the selection efficiency of superior promising families in early segregating generations of the durum wheat population. Two methods of selection were evaluated, namely, direct selection and indirect selection, by the selection index in the yield and its components. A comparison of mean performances for different traits among the four generations (F 2 , F 3 , F 4 , and F 5 ) revealed an increase in mean values for most traits with advanced generations from F 2 to F 5 , with some exceptions due to environmental factors. PCV and GCV were generally larger in magnitude for all studied traits in the F 2 generation as compared with the advanced generations F 3 , F 4 , and F 5 , indicating that the magnitude of the genetic variability persisting in this material was sufficient for providing a rather substantial amount of improvement through the selection of superior progeny. High heritability values over 50% for most studied traits across generations indicate a high magnitude of genetic variability and possible success in selection in early generations. Nine out of eleven selection indices were more efficient than direct selection for improving GY/P in the F 2 population. The highest predicted genetic gain from F 2 generation for GY/P was observed when selection index (I W123 ) was followed by selection index (I W2 ) and by selections for (I W12 ), (I W23 ), (I W1 ), and (I W3 ). Selection index (I W123 ), followed by I W12 and direct selection (I XW ), gave the highest actual genetic gains from the third generation for trait GY/P. Most indices showed a high discrepancy between predicted and actual genetic gain as GY/P; this was due to the interaction between genetic effects and large effects of environmental factors. The maximum predicted genetic advance from F 3 and F 4 generations for GY/P was achieved when selecting directly (I XW ) in F 3 followed by selection indices (I 123 ). While maximum actual genetic advance from F3 and F4 generations for GY and P was achieved when using selection indices (I 123 ), followed by (I W2 ), and then direct selection (I xw ). Deviations of the actual genetic advance from the predicted advance from the F3 and F4 generations showed positive and large values in most procedures.