Caractérisation cytogénétique classique et moléculaire de trois espèces endémiques du genre Hedysarum L.

Abstract

The first cytogenetic data are presented for two diploid species (2n = 2x = 16): H. pallidum Desf. and H. naudinianum Coss. and a tetraploid species (2n = 4x = 32): H. perrauderianum Coss. and Durieu. These endemic species of Algeria and North Africa are fodder. The karyogram consists of 8 chromosome pairs; one pair is satellite in the diploid and 16 pairs among which two are satellites in the tetraploid. The constitutive heterochromatin, as thin and wide, intercalary and telomeric bands is revealed by C-banding. One to four heterochromatic B chromosomes were observed. Staining of metaphase chromosomes by chromomycin A3 shows bands of DNA rich in GC base, located in the short arm telomere pairs with satellites, which correspond to the nucleolar organizer regions. FISH revealed the existence of a locus in diploid and two loci in the tetraploid of each family of ribosomal genes (5S and 35S). 5S signals are observed in H. pallidum (2x) in centromeric region, and in H. naudinianum (2x) and H. perrauderianum (4x) in telomeric region. In all three species studied, the loci 35S are located on satellifère pairs in secondary constrictions and NORs. The majority of bands CMA+ are also DAPI+.The similarity of certain chromosome pairs and presence of univalents, trivalents and tetravalents suggest an autotetraploid origin of H. perrauderianum species.The genome size of 2C = 1.5 pg in H. pallidum, 3.36 pg in H. naudinianum and 6.64 pg in H. perrauderianum. The karyotype analysis, organization of heterochromatin, ribosomal genes and genome size, it can be concluded that H. perrauderianum is nearest of H. naudinianum than H. pallidum.