American-Eurasian J. Agric. & Environ. Sci., 15 (3): 462-469, 2015 ISSN 1818-6769 © IDOSI Publications, 2015 DOI: 10.5829/idosi.aejaes.2015.15.3.12561 Corresponding Author: Muhammad Abdul Rehman Rashid, Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad. Pakistan. E-mail: rashidpbg@hotmail.com. 462 Nature of Gene Action for Certain Agronomic Characters in Gossypium hirsutum L. Farah Naz Kaleri, Muhammad Abdul Rehman Rashid, 1 2 Shahnawaz Mari, Zahoor Ahmed Soomro and Siraj Ahmed Channa 1 1 1 Department of Plant Breeding and Genetics, Sindh Agriculture University Tandojam-70060, Pakistan 1 Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan 2 Abstract: An experiment was conducted to investigate the gene action for plant height, GOT% and seed index of five commercial varieties and ten direct crosses in Randomized Complete Block Design with four replications during kharif 2004. Results revealed that parent Acala-P was good general combiner for plant height and GOT% 3 whereas DPL-25 and DPL-7340-424 were good general combiner for seed index. Cross Qalandri×Sarmast and Qalandri×Acala-P was the best combiner for plant height and seed index respectively while Acala-P ×DPL-7340- 3 3 424 was best specific combiner for GOT%. Further results revealed that plant height, seed index and GOT% were controlled by over dominance type of gene action. Regression line and Fr values confirm the gene action for the studied traits. Seed index and GOT% were controlled by one group of genes whereas plant height was controlled by three groups of genes. Key words: Gossypium hirsutum L. Gene action Diallel mating Agronomic traits INTRODUCTION The present study was designed to evaluate the Crop improvement is a one of the goals accomplished from commercially cultivated cotton varieties. The half by higher degree selection of genotypes with extra diallel crossing pattern was applied to achieve required ordinary performance. A significant variation in results. population is the main requirement for selection of superior plants which can attain by intercrossing of MATERIALS AND METHODS unrelated genotypes followed by phenotypic selection. The selection of parental lines for breeding of a specific The experiment was conducted during the kharif trait always based on the type and extent of genetic season of 2004 at the experimental field of Botanical control for that specific trait which can directly influenced Garden of Plant Breeding and Genetics, Sindh Agriculture by different environmental factors. University, Tandojam. Five parental varieties of There are several mating systems have been Gossypium hirsutum L. (Qalandri, Acala-P , DPL-25, designed to dissect the genetic and environmental control Sarmast, DPL-7340-424) were grown and crossed inter of complex quantitative traits. Diallel crossing is one of specifically in half diallel mating system. Three seeds per the most common adapted mating systems for crop hill for parental lines and ten F genotypes were sown by improvement. The diallel analysis proposed by Jinks [1] dibbling method in Randomized Complete Block Design and Hayman [2, 3, 4, 5] endeavors to dissect the total (RCBD) with four replications and thinned to one seedling variation, in genotypic and environmental components per hill to ensure uniform stand of only one plant per hill. and it further sub-divides genotypic variation, into The 30 cm plant×plant and 75 cm row×row distance was additive and dominance components. These values can maintained. All the standard cultural practices were be used to draw inference about the genetic system. applied. This method provides unique information about the Ten guarded plants per genotype were randomly nature of genetic system and together it clearly resolves selected and tagged from each replication. At maturity the mechanism of inheritance. data was collected for plant height (cm), seed index and inheritance pattern of plant height, GOT% and seed index 3 1