Karyotype analysis in Allium roseum L. (Alliaceae) using fluorescent in situ hybridization of rDNA sites and conventional stainings

Abstract

In North Africa, Allium roseum L. has been treated as a polymorphic species comprising 12 different taxa. More than 80 individuals in the Allium roseum complex were sampled from 20 populations at different localities in Tunisia and investigated karyologically. Basic chromosome number was confirmed as x = 8. Three cytotypes, diploid (2n = 2x = 16), triploid (2n = 3x = 24), and tetraploid (2n = 4x = 32), were found. Polyploidy was recorded for the first time for this species in Tunisia. Most of the populations were diploid (17 populations), whereas two populations were tetraploid and only one was triploid. The chromosome set of studied populations is nonuniform at the species level and within cytotypes. The 45S and 5S ribosomal genes (rDNA) were visualized by fluorescent in situ hybridization for the A. roseum polyploid complex. The diploid showed three loci 45S rDNA; the triploid and tetraploid showed 9 and 12 signals, respectively. However, 5S rDNA showed 2 signals for the diploid genome and 4 signals for both triploid and tetraploid. The 45S rDNA results showed intra- and interpopulational numerical variation. However, the data obtained with the 5S rDNA genes revealed a highly conserved distribution of these ribosomal families in the chromosomes of individuals from each population, as well as among the analyzed populations.