Citotaxonomia de espécies da tribo Vernonieae Cass. (Asteraceae Bercht. & J. Presl) ocorrentes em Pernambuco

Abstract

The Asteraceae family Bercht. & J. Presl has 1,500 genera and about 30,000 species distributed throughout the world. Although cosmopolitan, occurring predominantly in non- forest environments, presenting the main characteristics inflorescences into chapters, inferovariadas flowers and stamens with connate anthers. In Brazil, the Asteraceae family represents approximately 300 genera and 2,000 species. The Vernonieae tribe has great economic, medical and ecological importance. However, their taxonomy is very complex problems of delimitation of species. The karyotype analysis by cytotaxonomy, citoevolutivos assists in understanding the events involved in the modifications of the genome. The parameters used in this type of study represent important tools for taxonomy. Cytotaxonomic studies require, in addition to data such as number and chromosome morphology, the information derived from cytogenetic techniques such as differential staining pattern of distribution and amount of constitutive heterochromatin, cytochemical differentiation of heterochromatin by fluorochromes, the identification of repetitive regions or unique sequences by in situ hybridization, among others. To characterize the karyotype was analyzed CTHC, IC, BC, BL, R, CMC, A1 and A2 of eleven species of Vernonieae tribe (Asteraceae), and a study of the location and distribution of constitutive heterochromatin and 45S rDNA sites in karyotypes of six species of these species. Despite the variation in chromosome number of 2n = 18 to 2n = 60, the morphometric data showed karyotypes for all species with symmetrical predominance of metacentric chromosomes. The chromosome size ranged from 1.0 to 4.09 μm. The total chromosome length ranged from 58.31 μm in Pithecoseris pacourinoides to 192.70 μm in Blanchetia heterotrichia. Although these data showed high similarity between the karyotypes studied with respect to chromosome morphology for several genus was detected polymorphisms of chromosome number and size between species. There was a great diversity in banding patterns between the two species with numbers of CMA positive bands ranging from four to sixteen, while only two species showed DAPI positive bands in the terminal position of the chromosome arms. The 45s rDNA sites varied from two to six. The differences in the size and amounts of heterochromatic bands and 45S rDNA sites revealed may be related to small structural changes involved in the processes of evolution of karyotypes of Vernonieae tribe.