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Résumé :
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Three natural populations of Atriplex halimus L., located in three different climatic contexts, were studied using leaf characteristics (leaf area, leaf length to maximum width ratio, average width of the leaves and leaves to branches ratio) and iso-enzymatic markers. The study showed the existence of a highly significant morphological variability. This variability is more significant as the populations are geographically distant and located in different climates. The gradual character of this morphological variability along a climatic gradient, indicates that it is about a clinale differentiation. Clones obtained from semi-woody cuttings taken on the level of each population and placed in a common parcel have maintained the same leaf characteristics as the population sources, suggesting the genetic origin of this variability. The study of four iso-enzymatic systems confirms the existence of this variability. Thus, the percentage of polymorphic loci (P), the expected heterozygosity (He) and the mean number of alleles per locus (A) are of 85.71 %, 0.360 and 2.14, respectively. The Nei genetic differentiation index (Gst') obtained is of 0.11 and the fixation index Gis is of -0.271. The migration associated with a selection for their adaptation to the local conditions and/or the recent population bottlenecks can contribute to heterozygosity excess and to the installation of this ecoclinal variation observed.
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