Estimation of gene action for some quantitative traits associated with yield components in cotton

A line x tester analysis was conducted at Sakha Agricultural Research Station, Cotton Research Institute, Agricultural Research Center, Egypt, during two growing seasons (2023 and 2024), using six Egyptian cotton varieties as lines and three genotypes as testers. Results indicated that genotypes, parents, crosses, parents vs. crosses, lines, testers and line x tester were significant for all studied traits, except for uniformity index for tester. Lines showed the maximum contribution to the total variance for most studied characters, indicating a greater contribution from line parents than testers. Low values of narrow sense heritability were estimated for most characters, suggesting a minor role of additive variance in their genetic expression. Broad sense heritability (h2n%) ranged from 13.64% for boll weight to 71.93% for fiber strength. Estimates of phenotypic (PCV%) and genotypic (GCV%) coefficients of variability for various characters demonstrated slight discrepancy, indicating minimal environmental influence on the studied traits. Giza 94 and Australy 13 were identified as the best combiners for yield and yield components, whereas Giza 93 and Giza 96 were the best combiners for fiber quality properties.