Organisation du génome et étude palynologique de quelques espèces algériennes du genre Astragalus L

Abstract

This study contributes to a better taxonomical and evolutionary knowledge about four Astragalus taxa. Two of them are endemic of North Africa: Astragalus. armatus subsp. tragacanthoïdes and A. armatus subsp. numidicus. The third one is endemic of Sahara: A. pseudotrigonus and the last one is a widespread mediterranean, A. cruciatus. This approach seeks to explore the diversity upon karyological and palynological criteria. The cytogenetic study using different coloration technics, with or without fluorescence staining, established an identical chromosome number for all taxa 2n = 2x = 16. The Chromomycin coloration technic A3 and the fluorescence staining in situ hybridization (FISH) with double labeling, showed a variation in the number and the position of the GC-rich DNA regions associated or not to NOR'S. The study also showed the existence, in all taxa, of a single locus of 35S and 5S located at different positions. Nuclear DNA amount shows variation of the C value between the two subspecies of A. armatus, on one hand, and the other two taxa, on the other hand. The palynological investigations point out pollen variability in terms of size and form of pollen grains. These results provide basic information about the 4 taxa. We suggest further and exhaustive explorations on the entire genus in order to clarify its taxonomical and evolutionary specificities.