Physical mapping of 45S and 5S rDNA in two Sprekelia formosissima cytotypes (Amaryllidaceae) through Fluorescent In Situ Hybridization (FISH)

• Main Authors: José Manuel Rodríguez-Domínguez, Ernesto Tapia-Campos, Rodrigo Barba-Gonzalez
• Format: Article
• Language: English
• Published: Firenze University Press 2021-04-01
• Series: Caryologia
• Subjects: bulbous genus; karyogram; karyotypic formula; ornamental; plant chromosomes; ploidy level
• Online Access: https://riviste.fupress.net/index.php/caryologia/article/view/578
• ISSN: 0008-7114; 2165-5391

Chromosome number and position of rDNA were studied in plants of Sprekelia formosissima (Amaryllidaceae) collected in two populations with different ploidy level (2n=2x=60 and 2n=5x=150). The 5S and 45S rRNA loci were localized and physically mapped using two-color fluorescence in situ hybridization probes. The diploid (2n=2x=60) cytotype showed four loci for the 45S rDNA in two chromosome pairs (11 and 25) in telomeric position. The 5S rDNA was present in six loci of three homologous chromosome pairs (3, 13 and 19) in subtelomeric and telomeric positions. The chromosomes of the pentaploid cytotype (2n=5x=150) showed five loci for the 45S rDNA in telomeric position and five loci for the 5S rDNA in subtelomeric position. The karyotypic formula is 13m + 16sm + 1 st and the karyotype symmetry/asymmetry index is TF % = 34.67, AsK % = 65.32 and Syi % = 54.81, concluding that it is an asymmetric karyotype, bimodal with one distinctively large pair of chromosomes (10.42 µm) and a gradual decrease in the size of the other chromosome pairs, from the longest of 6.84 µm, to the shortest of 2.61 µm.