Sarhad J. Agric. Vol.26, No.3, 2010 373 COMBINING ABILITY IN MAIZE SINGLE CROSS HYBRIDS FOR GRAIN YIELD: A GRAPHICAL ANALYSIS IBNI AMIN KHALIL*, H. RAHMAN*, NASIR SAEED*, NAQIB ULLAH KHAN*, DURRISHAWAR*, IFFAT NAWAZ*, FARHAN ALI*, M. SAJJAD* and MOHAMMAD SAEED** * Department of Plant Breeding and Genetics, KPK Agricultural University Peshawar – Pakistan. E-mail: iakhalil@yahoo.com ** Department of Weed Science, Agricultural University Peshawar – Pakistan. ABSTRACT Combining ability estimates are important genetic attributes to maize breeders in anticipating improvement via hybridization and selection. This study sought single cross maize hybrids (SC) that could be used for the production of double cross maize hybrids (DC) for improved grain yield. Five commercial SC hybrids were crossed following a complete diallel fashion. All the DC hybrids along with self progenies were evaluated for combining abilities and to determine heterotic effects among the SC hybrids, using biplot diallel analysis at the KPK Agricultural University, Peshawar, Pakistan during 2007. General combining ability (GCA) and specific combining ability (SCA) effects were significant for the studied trait. Genotype hyb-4 was identified to be the best general combiner for grain yield, while high SCA effects were observed for crosses hyb-4 × HYB-3, hyb-4 × HYB-1 and hyb-5 × HYB-2. The graphical demonstration proposed by the biplot analysis provided an effective overview of GCA and SCA effects, mean performance in crosses, as well as grouping of similar genotypes on the basis of heterosis. Moreover, the biplot also provided an opportunity for assessing the interrelationship among the genotypes. Key Words: GGE Biplot, heterosis, hybrid maize, hybrid vigor Citation: Khalil, I.A., H Rahman, N. Saeed, N.U. Khan, Durrishawar, I. Nawaz, F. Ali and M. Sajjad. 2010. Combining ability in maize single cross hybrids for grain yield: A graphical analysis. Sarhad J. Agric. 26 (3): 373 - 379 INTRODUCTION Maize (Zea mays L.) is the most important crop after wheat in Pakistan’s Khyber Pukhtunkhuwa (KPK) where it was grown on about 0.51 million hectares with a total production of 0.96 million tons and average yield of 1.88 ton ha -1 (Anonymous, 2009). Maize is the primary crop in majority of the farming systems and also staple food of the rural population and poor resource farmers in KPK (Khan et al., 2003). The maize demand is considerably increasing due to poultry and livestock feed industries. Regardless of pronounced developments in maize research, the average maize grain yield in KPK (1.88 ton ha -1 ) is far below than national average yield (3.4 ton ha -1 ). The use of outdated open pollinated varieties is a major factor responsible for low grain yield of maize in KPK. The poor resource farmers can not afford the high cost single cross maize hybrid, and its use is almost negligible. It is confirmed that single cross hybrids are more productive than double cross hybrids, but keeping in view the low socio-economic status of the farming community, the use of double cross hybrids will be much better rather than use of low yielding open pollinated varieties. The double cross hybrids will obviously increase the per unit area production, which is also the primary objective in maize breeding programs. Maize breeding programs mostly involve hybridization, evaluation and selection of desirable genotype(s). In addition, the assessment of combining ability and heterotic effects are also elementary tools for selection of desirable genotype. The concept of combining ability was introduced by Sprague and Tatum (1942). Combining ability has a prime importance in plant breeding since it provides information for the selection of parents and also provides information regarding the nature and magnitude of involved gene action. The knowledge of genetic structure and mode of inheritance of different characters helps breeders to employ suitable breeding methodology for their improvement (Kiani et al., 2007). Diallel analysis is primary method and has been widely used to determine combining ability, heterotic responses and patterns in maize populations (Bertoia et al., 2006; Hallauer and Miranda Filho,