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Aegilops cylindrica species is one of the valuable gene pool of wheat for the understanding of salinitytolerance mechanisms such as Na+ exclusion. Eighty-eight Ae. cylindrica genotypes were collected from saline and non-saline areas of West Iran and used in this study. Physiological and morphological traits including shoot and root fresh and dry weights, leaf MDA and H2O2 contents, leaf and root Na+, K+ and Ca2+ concentrations, K+/Na+ and Ca2+/Na+ ratio of leaves and salinity tolerance index were evaluated. Salinity stress caused significant increases in MDA and H2O2 content, Na+, Ca2+ concentrations of root and leaves, while it led to significant decline in the remaining traits. Although dry matter correlated with leaf K+/Na+ ratio (R2 = 0.48), the regression coefficient was higher for leaf Na+ concentration (R2 = 0.58). The results of principal component analysis revealed two components (PC1 and PC2) which totally justified 52.47 and 48.02 % of total variations of the traits in control and salinity stress conditions, respectively. Three hypersalinity-tolerant genotypes originating from the shore areas resulted from shrinking of Uremia Salt Lake and depicted by the highest PC1, PC2, dry shoot weight and leaf K+/Na+ ratio as well as the lower Na+ concentration in leaves and roots. The high Na+ exclusion ability in roots and shoots of Ae. cylindrica genotypes open up new avenues for further analyses at the cellular and molecular levels to address the role of C genome as well as the complex relations between C and D genomes to cope with hypersalinity stress via ionic homeostasis.
Uremia Salt Lake, in North West Iran, has a hyper-saline water. A rare highly salinity-tolerant grass species, Aegilops cylindrica grows along its shores. Salinity tolerance of 44 genotypes of Ae. cylindrica, mainly collected from the Lake, was evaluated under control and 400 mM NaCl conditions using the physiological traits of plant height, dry weight, proline content, Na⁺and K⁺ concentrations as well as K⁺/Na⁺ ratio. To evaluate the association between microsatellite (EST-SSR and SSR) markers and salinity tolerance, 35 primer pairs were used. Results showed a significant variation in the 44 genotypes studied in terms of their traits except for proline content. Ten most salinity-tolerant genotypes were identified based on their ability to survive, to produce the highest dry weight, and to sustain the least leaf Na⁺ concentration under salinity stress. The very high negative correlation found between Na⁺ concentration and salinity tolerance revealed the importance of individual or a combination of Na⁺ exclusion and excretion mechanisms contributing to the hyper-salinity tolerance of these genotypes. Clustering analysis based on marker data divided the 44 studied genotypes into two groups that were consistent with their saline and non-saline geographical areas. Results of molecular markers showed that four microsatellite markers (Xgwm312, Xwmc170, Xgwm291 and Xgwm410) generated a distinguished banding pattern in ten most salinity-tolerant genotypes. These results supported previous reports on their linkage with Na⁺ exclusion genes (HKT1;5 and HKT1;4) in wheat, which provided further evidence of usefulness of both genes and the linked markers to the salinity tolerance of the halophytic grass family species.
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