Cytogenetic studies in herbertia sw. (iridaceae)

Abstract

— Conventional Feulgen staining, CMA/DAPI banding and FISH with 18–5.8–26S rDNA probe were used to determine chromosome numbers, karyotypes and physical position of GC or AT rich heterochromatin and rDNA sites in three South American species of Herbertia: H. lahue subsp. amoena, H. quareimana, and H. darwinii. The basic number of the genus is × = 7, but the analyzed taxa have different ploidy levels. The chromosome number was 2n = 14 for H. darwinii and 2n = 28 for H. quareimana. The two populations studied of H. lahue subsp. amoena did result in: 2n = 42 (Gualeguaychu) and 56 (Palma de Castillo). Chromosome size varied between 1.60 and 5 μm. The karyotypes did give with a total of 8 metacentric (m) + 6 submetacentric (sm) chromosomes for H. darwinii and 20 m + 8 sm chromosomes for H. quareimana. The two populations of H. lahue subsp. amoena showed with 26 m + 16 sm chromosomes and 36 m + 20 sm chromosomes. H. darwinii had a bimodal karyotype. H. darwinii showed one satellited pair whereas the remaining species two (always in short m chromosome arms). Moreover, the 2n = 56 population of H. lahue subsp. amoena one satellite on the long arms. No CMA−/DAPI+ bands were detected in any species, but CMA+/DAPI− bands associated with nucleolar organizing regions (NOR) were found in all cases. The locations of the 18–5.8–26S rDNA sites in all species coincided with CMA+/DAPI− bands. Our data suggest that karyotypic diversifcation in Herbertia included changes in chromosome number, symmetry, and number and position of NORs regions. © 2009 Taylor & Francis Group, LLC.