Sélection in vitro pour la tolérance au stress hydrique chez le blé dur (Triticum durum Desf)

Abstract

The in vitro evaluation of three durum wheat genotypes (Djenah Khetifa, Oued Zenati and Waha( to water stress tolerance simulated in vitro by different concentrations of PEG 6000 indicated significant differences among genotypes, PEG concentrations and their interactions for all the studied characters, indicating genetic variability in PEGsimulated drought stress. The osmotic pressure has negatively affected all parameters studied. However, cells that continue to grow under severe osmotic stress are considered as tolerant to water stress. In vitro screening for stress tolerance reveals the variety Djenah Khetifa as the most tolerant and Waha as sensitive. The studied traits can be recommended as suitable selection criteria for screening drought-tolerant genotypes. Three amplified and reproducible locus (gwm331, gwm335 and gwm427) were retained. These loci provided in total 78 monomorphic loci of which 69 were detected in somaclones. Five somaclonal variants (DKR1-S1, DKR1-S2, OZR1-S2, WR1-C3 and WR1-S1) were identified by only two SSR markers. Genetic variation rate was 21.74%. The presence of selective agent in the medium could explain the observed genetic variations. Somaclonal variation cannot always be detected at the gross morphological level. The selected SSR markers could be used to study the uniformity of plants obtained from tissue culture and varietal identification. Analysis of the proteins by a new two-dimensional diagonal electrophoresis approach named (D-2DE) followed by MALDI-TOF mass spectrometry has identified six differentially expressed proteins. For each variety, the level of mRNA expression of three candidate genes (globulin, GAPDH and peroxidase) and a ubiquitous (Actine) gene was determined by qRT-PCR. The amounts of mRNA of the three genes are partially correlated with the amounts of proteins. These genes were slightly up-regulated over the control. The D-2DE results were validated using Western blot analysis with specific anti-globulin and anti-glyceraldehyde in the embryogenic calli of wheat, in response to water stress. The proteins identified through this technique provide new insights as to how calli respond to osmotic stress. Our method of study provides an original and relevant approach that could contribute significantly to a better understanding of possible linkages between the abundance of specific proteins and the acclimation of durum wheat to water stress at the cellular level.