Citogenética da subtribo oncidiinae

Abstract

Oncidiinae is one of the largest subtribes of the Orchidaceae family, with approximately 1.524 species in the Americas with limited distribution to Neotropical zones. In Brazil, the subtribe Oncidiinae is represented by 49 genera and 360 species. There are many difficulties for the delimitations of the studies in Oncidiinae, in addition to the problems within the morphological limits, as, even to these adversities the recurrent variability in chromosomic numbers that is a representative resource for the group, showing the widest spectrum of variation within the orchids, from 2n = 10 to 168, but 2n = 56, 60 and 42 are the most common within a polyploid series based on x = 7, being considered a taxonomically complex subtribe. This study aims to accomplish the cytogenetic analysis of nine species of the subtribe Oncidiinae, based on the determination of their chromosome numbers and to identify the patterns of heterochromatic bands in their karyotypes through fluorochromes, cromomicina A3 (CMA) e 4´6-diaminidino-2-fenilindol (DAPI). Chromosomal numbers were found for the species Aspasia variegata 2n = 56, Gomesa hookeri 2n = 74, Gomesa ranifera 2n = 56, Gomesa sarcodes 2n = 56, Gomesa sp., Oncidium altissimum 2n = 56,, Rodriguezia lanceolata 2n = 40, Rodriguezia venusta 2n = 42 e Trichocentrum fuscum 2n = 22. The chromosome numbers found in this study are new counts for the species A. variegata, G. hookeri, G. ranifera and T. fuscum. In the analyzed species three types of heterochromatic bands were found: CMA+/DAPI-, CMA-/DAPI+ and CMA+/DAPI0. The presence or absence of these types of bands, such as the number and location on chromosomes are variable in karyotypes, allows cytotaxonomic differentiation of all species, even those that are the same or equal to the chromosome or if they are morphologically used and unique phylogenetics.