Assessment of yield, yield-related traits and drought tolerance of durum wheat genotypes (Triticum turjidum var. durum Desf.)

The main objective of this study was to evaluate 11 durum wheat breeding lines and three checks [ two durum (Zardak and Saji) and one bread (Sardari) wheat] based on grain yield, agronomic traits and drought tolerance indices under rainfed and irrigated conditions in the west of Iran during the 2008-09 cropping season. A completely randomized block design with three replications was conducted for each environment. Based on grain yield under rainfed and irrigated conditions drought tolerance indices i.e., stress tolerance index, stress susceptibility index, tolerance, yield index, yield stability index, mean productivity and geometric mean productivity were calculated. The results of analysis of variance for relative water content, plant height, biomass, number of grains per spike and grain yield in rainfed and irrigated conditions indicated that genotypic differences were highly significant (P<0.01). A positive and significant correlation was observed between yield under irrigated (Yi) and rainfed (Yr) conditions and mean productivity (MP), geometric mean productivity (GMP), and stress tolerance index (STI). Based on principle component analysis a significantly positive correlation was observed between stress susceptibility index and tolerance. These indices were able to select the susceptible genotypes (i.e., G8, G2, G3, and G7). The check cultivars (Zardak and Sardari) and G5 were more stable and related to the rainfed environment while genotypes G11 and G4 were highly adapted to the irrigated conditions. Cluster analysis classified the genotypes into three groups i.e., resistant, susceptible and tolerant to drought conditions. In conclusion, this study showed that drought stress reduced the yield of some genotypes while others were tolerant to drought, suggesting genetic variability of drought tolerance in this material. Therefore, breeders can choose better (i.e., more stress-resistant) wheat genotypes based on some indices (e.g. MP, GMP and STI).