Wheat storage protein, gluten, confers elasticity and extensi- bility essential for bread making. It contributes 80 - 85% of the total flour protein (Shewry et al. 1995). Gliadins and glutenins are two prolamine groups of gluten with their composition and interaction contributing towards visco-elastic properties of gluten. The glutenin fractions form long chains of polypeptides linked by disulfide bonds. These consist of low molecular weight (LMW) glutenin subunits and high-molecular-weight (HMW) glutenin subunits (Payne and Lawrence 1983). It has been well established that high molecular weight glutenin sub- units have the largest effect on the bread-making quality despite the fact that they constitute only 10% of the total storage pro- teins as compared to LMW-GS which contributes 40% (Payne et al. 1987). Allelic variation in HMW-GS composition was found to be strongly correlated with differences in bread-making quali- ty (Shewry et al. 1995). Additionally, they also serve as reliable genetic markers for exploring genetic diversity in wheat. Therefore, the analysis of HMW-GS is a pre-requisite and important criterion in breeding for bread-making quality improvement. The genetics, biochemistry, and structure of these HMW-GS have been copiously studied by several workers (Anjum et al. 2007). Genes encoding HMW-GS are present at Glu-1 loci located on the long arm of chromosomes 1A, 1B, and 1D and are identified as Glu-A1, Glu-B1, and Glu-D1. Each locus has two tightly linked genes encoding two different subunits of high and low molecular size termed as x- and y-type, respectively, but Awais Rasheed ( ) E-mail: awaispbg@gmail.com 1 The Korean Society of Crop Science J. Crop Sci. Biotech. 2012 (March) 15 (1) : 1 ~ 7 RESEARCH ARTICLE DOI No. 10.1007/s12892-011-0088-1 Allelic Variation and Composition of HMW-GS in Advanced Lines Derived from D-genome Synthetic Hexaploid / Bread Wheat (Triticum aestivum L.) Awais Rasheed 1 *, Tariq Mahmood 1 , Alvina Gul Kazi 2 , Abdul Ghafoor 3 , Abdul Mujeeb-Kazi 4 1 Plant Biochemistry and Molecular Biology Laboratory, Department of Plant Sciences Quaid-i-Azam University Islamabad, Pakistan 2 Atta-ur-Rehman School of Applied Biosciences (ASAB), National University of Science and Technology (NUST), Islamabad, Pakistan 3 National Agricultural Research Center, (NARC), Park Road, Islamabad, Pakistan 4 National Institute for Biotechnology and Genetic Engineering (NIBGE) Faisalabad, Pakistan Received: October 25, 2011 / Revised: December 29, 2011 / Accepted: January 25, 2012 Ⓒ Korean Society of Crop Science and Springer 2012 Abstract The objective of this study was to identify allelic variations at Glu-1 loci of wheat (Triticum aestivum L.) advanced lines derived from hybridization of bread wheat and synthetic hexaploid wheats (2n = 6x = 42; AABBDD). Locally adapted wheat genotypes were crossed with synthetic hexaploid wheats. From the 134 different cross combinations made, 202 F8 advanced lines were selected and their HMW-GS composition was studied using SDS-PAGE. In total, 24 allelic variants and 68 HMW-GS combinations were observed at Glu-A1, Glu-B1, and Glu-D1 loci. In bread wheat, the Glu-D1 locus is usually characterized by subunits 1Dx2+1Dy12 and 1Dx5+1Dy10 with the latter having a stronger effect on bread-making quality. The subunit 1Dx5+1Dy10 was predominantly observed in these advanced lines. The inferior subunit 1Dx2+1Dy12, predominant in adapted wheat germplasm showed a compara- tive low frequency in the derived advanced breeding lines. Its successful replacement is due to the other better allelic variants at the Glu-D1 locus inherited in these synthetic hexaploid wheats from Aegilops tauschii (2n = 2x = 14; DD). Key words : allelic diversity, Glu-1, HMW-GS, SDS-PAGE, synthetic hexaploid wheats Introduction