Electronic Journal of Plant Breeding, 4(1): 1027- 1033 (Mar 2013) ISSN 0975-928X http://sites.google.com/site/ejplantbreeding 1027 Research Article Diallel-cross analysis of grain yield and stress tolerance-related traits under semi-arid conditions in Durum wheat (Triticum durum Desf.) HANNACHI Abderrahmane 1 , FELLAHI Zine El Abidine 1 , BOUZERZOUR Hamenna 2 and BOUTAKRABT Ammar 3 . 1 National Institute of Agricultural Research, (INRAA), Setif Agricultural Research Unit, 19000 (Algeria). 2 Faculty of Life and Natural Sciences, Ecology and Plant Biology Department, University Ferhat Abbas Setif 1, 19000 (Algeria). 3 Faculty of Agro-veterinary and Biological Sciences, Agronomy Department, University Saad Dahlab Blida, 09000 (Algeria). Email: abderhannachi@yahoo.fr (Received: 22 Jan 2013; Accepted: 08 Feb 2013) Abstract Half-diallel analysis with six genotypes of durum wheat was conducted for grain yield, yield components and agronomic traits related to abiotic stress tolerance. Aim of this study is to identify best parents for hybridization. Cultivar Guemgoum Rkhem proved to be best general combiner for number of days to heading, straw yield, plant height and thousand-kernel weight. Gaviota durum was best combiner for number of grains per spike, and cultivar Ofanto for Chlorophyll content and harvest index. Waha proved to be a poor general combiner for flag leaf area, straw yield, plant height and thousand-kernel weight. Mexicali 75 /Guemgoum Rkhem cross is best suited to improve earliness, straw yield, plant height, and grain yield. Narrow-sense heritability was low for grain yield. Waha//Zenati Bouteille/Flamingo and Waha/ Guemgoum hybrids showed significant mid-parent heterosis for grain yield. Keywords: Durum wheat, diallel, combining ability, gene action, heterosis. Introduction Producing more cereals is becoming an urgent task for Algerian agricultural sector. In fact, Algeria needs to import, in near future, more than 11 million tons of cereals to cover the demand of an overgrowing population. To produce more cereals, the prevailing environmental constraints must be mastered and adequate producing technologies put forward. This is not the case of Algeria where the main cereal producing zones are characterized by harsh and variable climate and soils with continuous fertility declining due to decades of mining agriculture (Lahmar and Ruellan, 2007). Option to increase cereals production by expanding the area under cultivation has already been exploited, leaving the alternative to tentatively increase production per unit of cropped area; either through irrigation or through adoption of high yielding and stress resilient cultivars (Chennafi et al., 2006; Benmahammed et al., 2010). Increasing cereal production through genetic improvement is appealing. Besides grain yield, which represents the ultimate selection objective, a number of yield-related and stress tolerance- related traits have received much attention, such as chlorophyll content, flag leaf area, days to heading, plant height, straw yield, harvest index, 1000-kernel weight, peduncle length, grains per spike and spikes per plant. Early maturity is an important breeding objective in durum wheat (Triticum durum Desf.) under semi- arid growth conditions. Earliness minimizes the effect of terminal heat and drought stresses on plant, as short-cycle cultivars grow mostly under more favorable conditions than their long-cycle counterparts (Wiegand and Cuellar, 1981; Al- Khatib and Paulsen, 1984; Przulj and Mladenov, 1999). Under rainfed growth conditions of the Algerian eastern high plateaus region, tall wheat cultivars are preferred, because of better seedling emergence and ease of harvest. They offer the possibility to remove enough straw for animal feeding and bedding, while still keeping adequate residues for soil protection against wind and water erosion, as no-till sowing is slowly gaining acceptance in the region (Chennafi et al., 2011). Grain yield was found to be highly associated with harvest index, biological yield, thousand- kernel weight and number of productive tillers per plant, suggesting the use of these traits, individually or combined in an index, as selection criteria for yield improvement (Richards et al., 2002;Verma and Srivastava, 2004; Condon et al., 2004; Moragues et al., 2006). Grain yield and traits controlling stress tolerance are complex polygenic characters, sensitive to environmental changes, showing low response to selection (Ferdous et al., 2010). Improvements of such traits rely upon identification of genetically superior and suitable genotypes and their exploitation through either heterosis breeding or pedigree breeding. Selection of parents and crosses is based on knowledge of the magnitude and the nature of the genetic variances available in the base population. The present study was conducted with the objectives of determining general and specific combining ability of traits of agronomic interest in durum wheat and