الفهرس 
Introduction
Genetic materialsOnly 14 pages are availabe for public view
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Abstract
Introduction: In Egypt, cotton breeding programs and genetical studies on cotton are aimed to increase fiber quality as well as improving yield capacity and maturity earliness. Plant breeders have been continually searching for more efficient methods to screen and evaluate the large segregating populations. The purpose of this study: is to investigate the relative efficiency of singleseed descent, pedigree and bulk population selection procedures in improving of some economic characters in cotton and maintaining genetic variation. Materials and methods: This study was carried out at the farm of Sakha Agricultural Research Station, Kafr EL Sheikh Governorate, Cotton Research Institute, Agricultural Research Center, during the successive growing seasons, 1999, 2000, 2001, 2002 and 2003 to compare the efficiency of different selection methods for improving some economic characters in three crosses [(Giza 88 X TNB1), (Giza 85 X TNB1) and (Giza 45 X Kar.2)]. To comparing the respective lines derived by SSD, PD and BP procedures, field experiment was set up in the growing season of 2003. The selected lines by each method were evaluated in a randomized complete block design with three replications. Results and discussion: The achieved results of this study could be summarized in the following points : *Tests of significance of the mean squares cleared that the differences among lines derived by pedigree procedure were significant for all the studied traits except for number of the vegetative branches/plant, number of the total nodes/plant and fiber strength for the lines derived from second cross (Giza 85 X TNB1). Generally, the significance of mean squares of lines selected by each procedure suggested that the planned comparisons and the determination of the efficiency of selection procedures for all studied characters are valid. * The results revealed that the pedigree selection method (PD) proved to be the best among the three procedures applied in the present study. The best ratio of superior lines than the midparents for most the studied characters was detected in the pedigree selection procedure (PD) and the bulk population selection procedure (BP). * Highly significant values of genotypic variance ((Sv(B2g) were detected in the pedigree selection procedure (PD) than in the bulk population selection procedure (BP) and single seed descent procedure (SSD), respectively for all studied characters in the three crosses. High values of expected genetic gain as percentage of mean ((SE(BG) were found to be associated with high and moderate values of heritability estimates in broad sense in most of studied characters, indicating that the phenotypic expression of these characters were indicative of their genetic behaviour, so selection for these characters may be highly effective. * In general, it could be concluded from all previous results that the selection procedures applied were effective and successful for selecting the best lines and the phenotypic expression of these characters were indicative of their genetic behaviour, so the selection procedures for these characters may be highly effective and suitable to produce a superior lines depending on the characters under study and the genetic background of started materials.