Citogenética da Subtribo Laeliinae (Orchidaceae: Epidendroideae): Regiões heterocromáticas e localização do DNA Ribossomal

Abstract

Subtribe Laeliinae comprises about 1500 species and 50 genera. It is a strictly Neotropical group, widely distributed in tropical and subtropical regions. This study examined the cytotaxonomy of 20 species of the subtribe Laeliinae and one species of the Poneriinae, using banding techniques with CMA / DAPI staining and FISH with 5S and 45S rDNA. Most of the species presented 2n = 40, except two samples of Cattleya trianae, C. nobilior and Prosthechea faresiana, both with 2n = 42 and 2n = 80, respectively. The analysis of CMA / DAPI banding pattern and 5S rDNA location sites were quite variable and informative in karyotype differentiation of the subtribe Laeliinae. All species presented CMA+/DAPI- terminal bands in only one chromosome pair, except P. faresiana with six CMA+/DAPI- terminal bands. These bands were clearly heteromorphic in all species. CMA + / DAPI- Proximal bands were observed in all bifoliate Brazilian species of Cattleya, Besides C. nobilior, C. walkeriana, and one sample of C. trianae and C. warneri. In all species 45S rDNA sites were co-located with the CMA+/DAPI- terminal bands in a heteromorphic pair of chromosome complement. Our data suggests that the species karyotypes of the subtribe Laeliinae presents a great variability when using more refined techniques of fluorochrome banding and the use of molecular markers despite its apparent stability of chromosome number (2n = 40). These chromosomal markers were useful to corroborate phylogenetic groupings, identifying synapomorphies, or even to investigate the taxonomic relationships between species.