In 2007 season, line x tester analysis was used in the present study which included eight parental genotypes of Gossypium barbadense,L.; four of them belong to Egyptian cotton as lines i.e, Giza 45, Giza 88, Giza 86 and Giza 90, while, the other four genotypes used as testers were, Karshenky, Pima S7, Suvin and Australian. In 2008 season, experiment was designed in a randomized complete block with three replications at three locations i.e., Giza, Sakha and Pelqass to evaluate all genotypes, which involved eight parents and sixty F1's crosses. The aim of the present study was to estimate heterosis, combining ability, proportional contributions, genetic components and heritability for some characters.
Useful heterosis versus mid- and better-parents for most studied traits was found. The following crosses were demonstrated the best values of heterosis relative to better-parent for boll related characters i.e, cross; Giza 45 x Pima S7 and Giza 88 x Karshenky for boll diameter and boll length. The line Giza 45 was the best combiner for boll diameter and bract length. However, estimation of SCA effects showed that, the crosses; Giza 45 x Suvin and Giza 90 x Australian crosses had significant SCA effects for boll length. Proportion contributions of lines x tester interaction were higher than that of lines and testers for all studied characters, except lint percentage. Lines contribution was higher than testers contribution for the most studied traits. Genetic component denoted that the magnitude of non-additive genetic variance was higher than additive genetic variance for most studied traits. Heritability in broad sense values ranged from 6.98% for flower neck length to 97.47% for 2.5% span length. While, heritability in narrow sense values ranged from 0.00% for boll weight to 40.91% for lint percentage at combined data.
Phenotypic correlation coefficient was positive and significant between bract length and lint percentage for two crosses; Giza 45 x Pima s7 and Giza 90 x Suvin. Path coefficient analysis revealed that bract width and bract area and their joint effect were the greatest contributor to boll weight and lint percentage in the four crosses and could therefore considered as main selection criteria in cotton breeding program.