ANÁLISE DO PADRÃO DE DISTRIBUIÇÃO DA HETEROCROMATINA EM SETE ACESSOS DE Citrus

Abstract

Heterochromatin was considered as "junk DNA" for many years, until studies indicated its properties and functions in the genome. In genera such as Citrus, which has all species with 2n = 18 and high hybrid indexes, heterochromatin is used in cytogenetic studies to characterize and differentiate species according to the distribution of heterochromatic bands. The objective of this work was to analyze seven accessions of Citrus by their heterochromatic distribution. The accesses were analyzed by CMA/DAPI and classified according to the types of chromosomes that are found in Citrus species. All species maintained the CMA+/DAPI- pattern in heterochromatic bands, where all eight types of chromosomes were found. There were species with a very similar karyotype such as C. hystrix and C. longispina, C. iwaikan and C. kamikan, and others that were distinguished from the others (C. natsukiu, C. taiwanica and C. webberi), but in general all presented different karyotypes formulas. Each access presented particularities on specific chromosomes, such as heteromorphism of bands (larger or smaller bands than others), partially decondensed bands, etc. Band heteromorphism and lack of pairs of homologous chromosomes may indicate that these accessions are all of hybrid origin. From the karyotype formulas it was possible to make a parental connection of the accessions with the possible pure parental However analyzes using fluorescence in situ hybridization (FISH) others cytotaxonomic markers are necessary to confirm that hypothesis. The analyzes show that all accesses are great models for evolutionary studies within the Citrus group.