Karyotype analysis of Placea amoena Phil. (Amaryllidaceae) by double fluorescence in situ hybridization

Abstract

—Placea Miers ex Lindley is an endemic genus of Chile. There are between 3 and 6 species cited for Chile. P. amoena Phil., is a beautiful plant with red tepals and it is growing in the Province of Illapel in Región IV. We identify the physical localization of gene clusters of 5S and 25S rDNA in Placea amoena by double fluorescence in situ hybridization (FISH). P. amoena is 2n = 16, with the chromosome set 2m + 5sm + 1st. The ratio of the longest pair/shortest pair (R) is 2.60 with a karyotype asymmetry index (AsI %) of 63.15. Signals of 5S and 18/25S rRNA genes are seen in 5 of the 8 chromosomal pairs. Chromosome 1 has a 5S rDNA location terminal in the short arm; chromosome 2 contains the same localization, but in a position nearer the centromere; chromosome 3 shows no rDNA localizations; chromosome 4 has two signals, both in the terminal part of the short arm, the 18/25S rDNA at the tip of the arm and 5S rDNA inmediately below it; chromosome 5 has only one 18/25S rDNA signal terminal portion of the short arm; chromosomes 6 and 7 show no localizations; chromosome 8 contains one 18/25S rDNA signal distal in the short arm. The homologues of the long arm of chromosome pair 2 was polymorphic in the length. It would be of interest to localize 5S and 18/25S rRNA in the other species of Placea through in situ hybridization to help clarify the taxonomic position of each taxa. © 2004 Taylor & Francis Group, LLC.