Available online at www.scholarsresearchlibrary.com Scholars Research Library Annals of Biological Research, 2013, 4 (3):113-122 (http://scholarsresearchlibrary.com/archive.html) ISSN 0976-1233 CODEN (USA): ABRNBW 113 Scholars Research Library Evaluation of drought tolerance indices in wheat recombinant inbred line population Mojtaba Nouraein 1 , Seyed Abolghasem Mohammadi 1,2* , Saeid Aharizad 1 , Mohammad Moghaddam 1,2 and Behzad Sadeghzadeh 3 1 Department of Plant Breeding and Biotechnology, Faculty of Agriculture, University of Tabriz, Tabriz, IRAN 2 Center of Excellence in Cereal Molecular Breeding, University of Tabriz, Tabriz, IRAN 3 Dryland Agricultural Research Institute (DARI), Maragheh, IRAN _____________________________________________________________________________________________ ABSTRACT In a two years experiment, 149 bread wheat recombinant inbred lines (RILs) derived from a cross between of US variety Yecora Rojo and Iranian local genotype NO.49 along with parental lines were grown under well-watered and water deficit stress conditions, imposed at panicle initiation stage. Eight drought tolerance indices including Stress Tolerance Index (STI), Mean Productivity (MP), Geometric Mean Productivity (GMP), Stress Tolerance (TOL), Stress Susceptibility Index (SSI), Yield Stability Index (YSI), Relative drought index (RDI), and Drought resistance index (DI) were used to identify high yielding and drought tolerant RILs. Significant and positive correlation was found between grain yield under stress condition (Ys) and STI, MP, GMP, SSI, YSI, RDI, as well as DI indicating the efficiency of these indices for screening drought tolerant genotypes. Grain yield under drought stress condition was associated with yield under well-watered condition (r = 0.66 ** and 0.84 ** in 2009 and 2010, respectively). Reduction in plant height due to water stress was negatively correlated with grain yield, biomass, spike length, grain number per spike, and 1000 grain weight in 2009 and yield reduction percentage in 2010. Among the drought tolerance indices, GMP showed higher correlation with grain yield (r = 0.94 ** and r = 0.97 ** ), biomass (r = 0.73 ** and r = 0.81 ** ), and harvest index (r = 0.7** and r = 0.76**) under stress condition in 2009 and 2010, respectively. The biplot based on components showed that the most appropriate indices to identify genotypes were GMP, MP, and STI. Key words: Drought, panicle initiation stage, potential yield, tolerance indices, water deficit _____________________________________________________________________________________________ INTRODUCTION Wheat is widely grown as a rain-fed crop in semi-arid areas, where large fluctuations occur in the amount and frequency of rainfall events from year to year and among sites within years [21]. In arid and semiarid regions with Mediterranean climate, wheat crops usually encounter drought during the grain filling period [10]. Therefore, wheat production and its sustainability are largely influenced by drought stress which cause reduced crop yield [32]. Drought is one of the most common environmental stresses worldwide that affects growth and development of plants through alternations in metabolism and gene expression [23]. It was estimated that about 65 million hectares of wheat grown area world-wide are affected by this environmental constraint and under water-limited environments, wheat yields are commonly reduced to 50 percent or even less of its yield potential under normal irrigation [6].