Abstract
Each of cotton varieties Halab90, SP8886, Verkana2, Stonvill 474 and Nazley87 (as males) were crossed to three other varieties (as females), respectively: (Cocker310, Deer22, Cocker5114), (Lachata, Dunn1047, Acala SJ2), (Halab33, Montana, Rekka5), (IK347, IK259, Mersoomy1), (Mersoomy4, Deltapine50 and Delatapine5409) using nested mating design. Parents and 15 hybrids among them were planted using randomized complete block design with three replications to study heterosis, general combining ability and estimate phenotypic variance components and some genetic parameters for traits: ginning outturn, lint index, fineness, 50% & 2.5% span length, fiber length uniformity, fiber strength and elongation. The results indicated than mean square of genotypes highly significant for ginning outturn, lint index and elongation, and mean square of males and female/male significant for the most traits. The varieties Cocker310, Cocker5114, Acala SJ2 and Montana seemed to have significant desirable general combining ability for larger number of traits. The cross (Halab90 x Cocker310) gave significant hybrid vigor for larger number of traits. Additive genetic variance values more than dominance one for: fiber fineness, 50% & 2.5% span length and elongation, and the reverse for the remainder traits, and the average degree of dominance exceeded one for all traits indicated the presence of over dominance except 50% 7 2.5% span length. The broad sense heritability low for fiber fineness and 2.5% span length, high for ginning outturn, lint index and elongation, and moderate for other traits, while narrow sense heritability low for ginning outturn, lint index and fineness, and moderate for other traits. The expected genetic advance was shown low for all traits (Ranged from 0.329% for lint index to 5.963% for fiber elongation).