IRANIAN JOURNAL of GENETICS and PLANT BREEDING, Vol. 3, No. 2, October 2014 28 Biplot Analysis of diallel crosses for yield and some morphological traits in durum wheat Davoud Sadeghzadeh-Ahari 1 , Peyman Sharifi 2 *, Rahmatollah Karimizadeh 3 , Mohtasham Moha- mmadi 4 1 Dryland Agricultural Research Institute, Iran, y, P.O. Box 119. 2 Department of Agronomy and Plant Breeding, Rasht Branch, Islamic Azad University, Rasht, Iran, Post code: 4147654919. 3 Dryland Agricultural Research Institute, Gachsaran Station, Iran, Post code: 7581818449. 4 Dryland Agricultural Research Institute, Gachsaran Station, Iran, Post code: 7581818449. *Corresponding author, E-mail: peyman.sharifi@gmail.com, Tel: 09112829197, Fax: 01333447060. Abstract Six varieties of durum wheat were included in a full diallel mating design during 2003-2004 and 2004-2005 cropping seasons in the farm of Mara- gheh Dryland Agricultural Research Institute (DARI), Iran. Parental durum wheat genotypes and their complete diallel progenies were grown in a randomized complete block design with two rep- lications in the growing seasons of 2005-06. The highest values of number of seeds per spike, one hundred seed weight and seed yield were ob- tained in Gerdish. The GCA effects indicated that Zardak was an ideal general combiner for one hundred seed weight, coleoptile length, number of germinated seeds, number of seeds per spike, growth vigor and radicle length. Crosses of Knd1149//68/ward × Waha and Zardak × Chehel daneh exhibited the highest value of seed yield and significant heterosis. Graphic analysis indicat- ed that the hybrid between Knd1149//68/ward and Waha was the best hybrid for seed yield, because it integrated the four genes (A2, D1, D2 and prob- ably D3) for seed yield. Zardak, Knd1149//68/ward and Gerdish can be used either as the best par- ents for selection programs based on their GCA effects, or as a superior parent in hybrid programs based on their SCA effects. Key words: Biplot, Combining ability, Diallel, Her- itability. INTRODUCTION Durum wheat (Triticum durum Desf.) is grown on about 14 million hectares, or 6% of the world’s total wheat growing area (USDA, 2009). It is the most im- portant cereal crop for making macaroni and other types of foods. The production of durum wheat in Iran is relatively smaller than bread wheat production (Karimizadeh et al., 2012) Diallel mating designs widely used to obtain infor- mation on the inheritance of quantitative traits, to select the best parental combinations for crosses and to de- termine the heterotic responses and heterotic patterns, are important tools in plant breeding programs (Griff- ing, 1956). The technique helps breeders for generating superior hybrids (Yan and Kang, 2003). This method has been utilized remarkably in wheat breeding pro- grams. The application of principal component (PC) biplot techniques for diallel crosses were suggested by Yan and Hunt (2002). Biplot approach based on diallel experimental data are used to estimate the general combining ability (GCA) and specific combining abil- ity (SCA) and to identify potential heterotic relation- ships among different genotypes (Yan and Hunt, 2002). A high degree of heterosis occurs when the parents are genetically divergent or unrelated and result in a hybrid that presumably is heterozygous at numerous loci in the genome (Krishnamoorthy, 2005). Two advantages of biplot analysis compared to other biometric diallel analysis are its graphical presentation and better inter- pretability of data, which greatly enhances ability to understand the patterns of data. While the conventional method of diallel analysis was designed to describe the