Ability, Heterosis and Genetic Parameters Estimates for Yield and Its Related Traits Using Line × Tester Mating Design in Egyptian Cotton (Gossypium barabadense L.)

This investigation was carried out at the experimental farm of Faculty of Agriculture, Alexandria University, during 2018 and 2019 summer growing seasons. The objectives of this study were to determine some genetic parameters of some cotton genotypes for yield and yield components traits under two levels of nitrogen fertilizer through line x tester mating design. Ten parental genotypes (seven lines and three testers) along with their 21 F1 crosses were arranged in two experiments of randomized complete block design (RCBD) with three replications. Genotypic, parental, crosses, parent vs crosses, lines, testers and line x tester variances were significant or highly significant for all the studied traits under both nitrogen fertilizer levels. The variance due to General combining ability (GCA) of parents (lines and testers) and specific combining ability (SCA) of crosses was significant for most of the studied traits, indicating the importance of both additive and dominance effects in controlling these traits. Values of GCA and SCA effects showed that the parents and some crosses gave desirable and significant GCA and SCA effects under two levels of nitrogen fertilizer. The high mean performance estimates and significant GCA effects were observed for the (G94 and G97) lines and (G90 x Aust.) tester for most of yield and yield components traits, so these parents can be used for generating good cotton hybrids. The highest values of mean performance, desirable SCA effects and highest heterosis values were detected in the combinations (G97 x (G90 x Aust.), G93 x (G90 x Aust.), G96 x (G90 x Aust.), (G92 x G86) and (G94 x G86) for the most studied traits under the two levels of nitrogen fertilizer (30 and 60 kg N/ feddan) and these crosses can be considered the promising crosses to be used in breeding program to produce new cotton hybrids and improve of yield and yield component traits.