MESSAOUDI Noura2021-07-072021-07-072021http://dspace.univ-msila.dz:8080//xmlui/handle/123456789/24736The objective of this study is, on the one hand, to study the mechanism of tolerance to abiotic stress in some varieties of wheat (Triticum sp.). To do this, a global strategy was followed, combining phenotypic and genotypic studies by integrating different agro-morphological, physiological, biochemical, and molecular characters. The study provided an overview of the behavior of 25 varieties of durum wheat (Triticum durum Desf.) with respect to water deficit and to distinguish the varieties least affected by this constraint. The results obtained following the statistical analyzes carried out demonstrated a large genotypic variability for the majority of the characteristics studied. Analysis of the links between the variables measured in the genotypes indicates that the yield is the result of three main components which are the number of ears, that of kernels / ear and the weight of the kernel. Principal Component Analysis (PCA) shows that productivity is related to high values for grain per plant yield, number of seeds per ear, weight of ears and plant height, while the traits of adaptation are high aboveground biomass, reduced leaf area, high plant cover temperature and low relative water content. The morpho-physiological parameters studied in the genotypes, subjected to the same conditions of water stress, made it possible to reveal a significant genotypic variability and significant differences exist between the lines evaluated and the treatment and for the interaction between "variety * treatment" for the variables measured. The results obtained indicate that from a morpho-physiological and biochemical point of view, cultivars develop different strategies to counter water stress. Thus under moderate stress, maintains a level of growth similar to that of the irrigated control. In contrast, most varieties are more sensitive to severe water stress. The results of the molecular analysis highlight the strategies adopted by the different varieties to counter water and salt stress. The expression of these genes remains; however, dependent on the genotype used the intensity and duration of the stress involved and the nature of the stress.Tolerance, Triticum sp, abiotic stress, characters, genesThesis