Caractérisation de la tolérance à la sécheresse chez le blé dur (Triticum durum Desf)

Abstract

Knowledge of the physiological characteristics, biochemical and agronomic processes involved in plant adaptation to abiotic stresses is a milestone in fight against drought. Forty varieties of wheat (Triticum durum) from various sources were used in this study. With three experiments, a semi-controlled test conditions, a field test and a controlled test in growth room, with each experiment, stressful conditions (rain or water deficit) and irrigated. In the first trial several physiological parameterswere studied on six varieties of durum wheat. However, the second trial was conducted in order to compare field production and performance of varieties studied in culture conditions, several measurements were made during development of the plant phenological traits, physiological such as water status of the plant (RWC and RWL) and osmotic potential, morphological parameters and yield and its components. A third experiment was conducted in this study to determine the genetic basis of phenotypic variation. This approach analyzes the statistical association between phenotypic variation and genetic polymorphism using molecular markers like SSR (Simple Sequence Repeat). The results show highly significant genotypic differences for all measured parameters. The recorded observations show that water deficit causes, in all varieties, a progressive decrease of chlorophyll and increased stomatal resistance resulting in a decrease in photosynthetic activity and consequently a decrease in production of dry matter. However, under the same conditions of water stress, introduced varieties have good ability to adaptations ompared to local varieties. Nevertheless the variety (Beliouni) is the variety most productive compared to other local varieties. Positive correlations were observed betweennet photosynthesis and production ofdry matter. And a significant effect stress and genotype was revealed in the second test, our results show that the water deficit causes a decrease in the relative water content and osmotic potential TRE (Po) of all varieties, which was adjusted by an accumulation of soluble sugarsand proline. This accumulation of osmoticums was very important, very well marked among varieties under stress. Concerning the molecular approach and the genetic association between genotypic and phenotypic variation. The results of this section have shown that phenotypic variation are highly significant, as revealed by a principal component analysis, describing 74% of total variation introduced by two axes ; CP1 and CP2. The hierarchical classification (cluster)show the distribution of genotypes according to their phenotypic variation, based on their origins. For association analysis, the results show that the markers used are significantly associated with the traits studied. The majority of these studied markers were significantly associated with the traits studied , located on chromosome4B. For productivity , three significant SSR markers were detected respectively associated: (WMS149 (p <0.01), WMS30_2) (p <0.05), WMC177_2 ( p <0.05) respectively with 68.94%, 99.46% and 49.74% of phenotypic variation, located on chromosome 4B, 3A and 2A. Also, the hypothesis of association of SSR with heading date (HD) was tested by the GLM (General Linear Model), two SSR markers were found significantly associated with HD they are: (WMS6(p <0.01) located on chromosome 4B, with 96.84% of phenotypic variation, and WMC445(p <0.05) on chromosome 5A with 32.46% of phenotypic variation. Our results also reveal a significant allelic diversity is characterized by high values of polymorphism information content (PIC), the mean value obtained for all primers was 74%, the highest ones were obtained for WMC177and WMC78markers with (94% and 93%), respectively, this is in agreement with the large number of alleles detected by these markers, these results reinforces and justify the choice to use these primers association analysis in our durum wheat varieties.