JOURNAL OF AGRICULTURE & SOCIAL SCIENCES 1813–2235/2005/01–2–129–132 http://www.ijabjass.org Combining Ability Analysis for Yield and Yield Contributing Traits in Bread Wheat SHAHID NAZIR 1 , ABDUS SALAM KHAN AND ZUFIQAR ALI Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad–38040 Pakistan 1 Corresponding author mail: shahidnazir97@yahoo.com ABSTRACT A 5 x 5 diallel cross involving wheat varieties LU-26S, 18172, 27HTN/1-54, DSN-5 and 243-1, was evaluated for general combining ability (GCA), specific combining ability (SCA) and reciprocal effects for various yielding traits like, flag leaf area, number of tillers per plant, spike length, number of spikelets per spike, number of grains per spike, 1000-grain weight and grain yield per plant. The study revealed that variance of components attributable to GCA, SCA and reciprocals effects were highly significant for all the characters studied. The GCA mean squares were larger than those of SCA for all characters except number of tillers per plant, number of grains per spike and 1000-grain weight. The higher magnitude of SCA than GCA for characters indicated that non-additive type of gene action was involved for the expression of the characters. Genotype 243- 1 was better general combiner for flag leaf area, tillers per plant, number of grains per spike and 1000-grain weight. Most of the crosses showing desirable significant SCA effects involved non-additive type of gene action. Key Words: Bread wheat; Combining ability; Diallel INTRODUCTION Wheat (Triticum aestivum L.) occupies a pivotal position among cereal crops. It is a leading grain crop of the temperate climate of the world, just like rice in the tropics. It is the dietary mainstay for millions of the people. It is a chief source of caloric and other valuable nutritive materials notably protein requirements of our people. To increase the yield potential of the wheat varieties information on the genetic mechanisms, like combining ability is of major importance. Sprague and Tatum (1942) defined combining ability and divided it in to general and specific combining ability. Combining ability analysis developed by Griffing (1956) has been extensively used to derive such information in F 1 generation. Its method I, and model I is the best in that it also gives the information for the effects of reciprocals. Singh et al. (1980), Bajwa et al. (1986), Malik et al. (1988) and Sattar et al. (1992) reported the both general and specific combining ability variances were highly significant for most of the characters indicating additive and non- additive type of gene action. While Mohy-ud-din and Shahzad (1998) and Khan and Ali (1998) reported significant general combining ability (GCA) variances for most of the characters. In addition, this analysis provides the nature and magnitude of various types of gene actions involved in the expression of qualitative and quantitative traits. The breeders are often facing problems of selecting those parental lines, which in different cross combinations can furnish higher frequency of most desirable segregants. To achieve this goal, knowledge of prepotency of parental lines for combining ability is very useful in selection of desirable lines. Most of the reports on combining ability analysis aimed at extracting as much basic genetic information as possible, and not specifically designed to apply the analysis in identifying crosses with superior performance for use in practical wheat breeding programme. Therefore the present study was undertaken to estimate the general and specific combining ability for yield and yield contributing traits in some wheat crosses. This information could be of great value for a successful wheat breeding programme to develop high yielding wheat genotypes. MATERIALS AND METHODS The present research work on combining ability studies for various plant characters was carried out in the experimental area of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad. The experimental material comprised of five varieties/lines of bread wheat (Triticum aestivum L.) viz., LU-26S, 18172, 27HTN/1-54, DSN-5, 243-1. The five parental lines along with their hybrids and reciprocals were planted in Randomized Complete Block Design with three replications. The hybrid seed including reciprocals and parents was sown in the field during crop season 2002-03, using the randomized complete block design with three replications. Each replicate had 25 lines and each line was 5-meter long. The plant-to-plant and row-to-row distance was 15 and 30 cm, respectively. The sowing was done by using a dibble. Two seeds per hole were sown which were thinned to single seedling per site after germination to ensure good plant stand. At the time of maturity 10 guarded plants from each line were selected at random and the data