91 Plant Omics Journal    2(2):91-97 (2009)  ISSN: 1836-3644 Genetic basis of some quantitative traits in upland cotton (Gossypium hirsutm L.) *Muhammad Amjad Ali, Amjad Abbas 1 , Muhammad Younas 1 , Tariq Manzoor Khan 2 and Hafiz Mumtaz Hassan 2 *Wheat Research Institute, Faisalabad, Pakistan 1 Agricultural Biotechnology Research Institute, Faisalabad, Pakistan 2 Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan *Corresponding author: Amjad.Ali2001@gmail.com Abstract Five cotton cultivars were crossed in a complete diallel to study the inheritance of different polygenic traits. Genotypic differences were found to be significant (P<0.01) for all the characters. Adequacy tests disclosed that data of all the parameters were fully adequate for genetic analysis except bolls per plant, staple length, fibre strength, and fibre fineness, which was partially or not adequate. Additive component of genotypic variation (D) was significant and predominant for plant height, sympodia per plant, staple length and fibre strength, while dominance effects (H 1 and H 2 ) were main controlling factors for of monopodia per plant, number of bolls, lint percentage and seed cotton yield. More dominant genes were revealed in the parents for sympodia per plant, lint percentage and seed cotton yield. The values of H 2 /4H 1 demonstrated asymmetrical and unequal distribution of dominant genes in the parents for all characters. Plant height, sympodia per plant, staple length and fibre strength exhibited high narrow sense heritability (h 2 n.s) due to the presence of additive gene action, whereas, monopodia per plant, number of bolls, lint percentage and seed cotton yield possessed low heritability. The genetic analysis suggested that plant height, sympodia per plant, staple length and fibre strength could be improved through sib family, pedigree and progeny selection, while exploitation of heterosis would be necessary to attain the genetic advancement in monopodia per plant, number of bolls, lint percentage and seed cotton yield. Keywords: Additive-dominance model; components of variation; multigenic traits; Gossypium hirsutum Introduction Despite of substantial progress made in other sectors, agriculture, by part, still has the pivotal position in the economy of Pakistan (Ali & Khan 2007b). Amongst the crops, upland cotton (Gossypium hirsutum L.) is very important. It sustains a lot of peoples in various fields such as textile mills, agriculture fields, ginning factories, small-to-large scale business and trade. Cotton accounts for 8.6% of the value added in agriculture and about 1.8 percent to GDP (Anonymous 2007). The crop was sown on the area of 3.075 million ha, 0.9 percent less than last year. The production of cotton is provisionally estimated at 13.0 million bales for 2006-07, lower by 0.1 percent over the last year’s production of 13.019 million bales. Lower production was attributed primarily to the 11 percent decline in area sown in Sindh due to excessive rains and floods (Anonymous 2007). It means that area under cotton cultivation is shrinking