First karyotype analysis, physical rDNA mapping, and genome size assessment in 4 North African Astragalus taxa (Fabaceae)

摘要

Four taxa of Algerian Astragalus L. were studied for their chromosome number, karyotype features, and genome size. Fluorochrome banding was done for detection of GC-rich DNA regions, fluorescence in situ hybridization (FISH) for physical mapping of 35S and 5S rRNA genes, and flow cytometry for nuclear DNA content. All the taxa present the same chromosome number (2n = 2x = 16) and single 35S and 5S rDNA loci, but their distributions on chromosomes are different. The GC heterochromatin pattern was different among studied taxa and an unusually high number of chromomycin-positive bands were observed in A. pseudotrigonus Batt. & Trab. The genome size differed between species, ranging from 2C = 1.39 pg in A. cruciatus Link. to 2C = 2.71 pg in A. armatus subsp. tragacanthoides (Desf.) Maire. No difference in nuclear DNA amount was detected between the 2 subspecies of A. armatus. Although Astragalus is a large genus comprising some 3000 species, such morphometric and molecular cytogenetic karyotype analyses, with genome sizes, are particularly scarce therein. Therefore, published genome sizes have also been compiled into one table.