Construction selection indices for the important traits of bread wheat cultivars (Triticum aestivum L.).

The study aimed to form an efficient statistical selection index of important traits by using fourteen cultivars of bread wheat under three levels of potassium oxide spraying (0, 1 and 2 %).The experiment performs in the winter season in 2018-2019 at the agriculture farm of Salahaddin governorate, Iraq (43.35 ֩ Longitude E and 34.27 ֩ Latitude N) by using R C B D in a split plot arrangement (spraying in main plot and cultivars in subplot) with three replications. Results concise Potassium spraying, cultivars and their interactions showed significant differences in grain yield, grain yield components and some quality traits. Though, cultivars didn't differ significantly in weak gluten. The construction selection index for the superior level of spraying potassium oxide (2%) revealed that genetic variations were significant and higher than environment variances in all studied traits except ash, strong and weak gluten content. The expected gain from selection was low and not significant for all studied traits except for protein and weak gluten percentage, though high heritability estimates. Superior selection index was I:1235 (1:grain yield, 2:plant height, flag leaf area and 5: protein content) result from comparing gain from selection for selected traits simultaneously with grain yield alone which possess higher relative efficiency (102.32) than others selection indices. The highest value of the best selection was in Ibaa99 (5.724) followed by Sham6 (5.601). Selection growth characters: plant height, flag leaf area and protein content are important in improving grain yield especially the Ibaa99 cultivar. [ABSTRACT FROM AUTHOR]