Combining Ability of Upland Cotton Genotypes over F2 Generation Of 7x7 Diallel Cross

Cotton varieties, Coker30, SP8886, Lachata, Montana, Halab33, AC22 and Gourd26, and all their F₂ half diallel crosses were planted at Al-Hawija, Kirkuk Governarate in 1^st of May, 2012 using randomized complete block design with three replications to study general and specific combining abilities for parent and crosses respectively and estimation of phenotypic variance components and some genetic parameters for characters: plant height, number of fruiting branches per plant, number of bolls per plant, boll weight, seed index, lint index and seed cotton yield per plant. results obtained from analysis of variance showed that mean square of genotypes, general and specific combining ability was proven to be significant for all characters except that of genotypes and general combining ability for number of fruiting branches. The variety Lachata appeared as a good general combiner, and (SP8886 x Halab33), (Lachata x Gourd26) crosses as good specific combiners for larger number of characters. The variances (additive, dominance and environmental) appeared significant from zero for all characters, except dominance one for number of fruiting branches, and the dominance variance was higher than additive one for all characters. The total genetic variance was high as compared with environmental variance for all characters except number of fruiting branches and boll weight. The average degree of dominance was higher than one for all characters indicating the presence of over dominance with exception of number of fruiting branches. Narrow sense heritability ranged from 17.96% for lint index to 35.24 for boll number, as was low for boll weight, seed index and lint index and moderate for other characters, while broad sense heritability ranged from 7.64% for number of fruiting branches and 85.12% for boll number, as was low for number of fruiting branches and boll weight, moderate for plant height and high for other characters. Genetic advance as percent from character mean in the third generation was moderate for boll number and seed cotton yield where reaches in them 16.227% and 12.996 respectively, while it was found to be low for other characters.