Citogenética clássica e molecular de espécies do gênero Manihot Miller (Euphorbiaceae Juss.)

Abstract

The Manihot genus belongs to the family Euphorbiaceae and has 100 species. The central parte of Brazil as South West of Goiás and Minas Gerais are considered the greatest center of diversification, followed by the Southeast of Mexico, northeastern of Brazil and southeastern of Mato Grosso. Manihot originates from the Americas being distributed from the United States to Argentina. M. esculenta Crantz is the most important of all species kind of economic point of view, as one of the most widespread food crops in the world. Manihot is a taxonomically complex genus by having large botanical plasticity beyond natural interspecific hybrids due to poor reproductive isolation barrier. To better understanding this genus in the cytogenetic, this study aimed to characterize five species of Manihot by employing the conventional technique, duble staining with CMA and DAPI, fluorescence in situ hybridization (FISH) and immunostaining. In general, the data showed a strong similarity between studied species. The diploid number corresponds to 2n = 36 chromosomes with small size, on average 2.5 micrometers and morphology of metacentric to submetacentric. The condensation pattern was always proximal profásico, but with minor differences in the time of condensation between arms of some chromosomes of the karyotype. With the exception of M. maracasensis e M. dichotoma, which showed 12 heterochromatic bands (CMA+) showed with chromomycin, all the others species showed six terminal CMA+ bands. In all species, there was always the presence of other small telomeric bands weakly stained with CMA+. Fluorescence in situ hybridization with ribosomal DNA probes showed six bands or regions of the 45S rDNA, always corresponding to heterochromatic bands CMA+. Only two blocks of 5S rDNA subterminal were observed for all species. However, we observed polymorphism for the species M. dichotoma showed that seven regions of 45S rDNA. Immunostaining with anti-H4K5ac and anti-H3K27me3 antibodies was detected as bands in metaphase chromosomes terminal of euchromatin and decondensed chromatin of interphase nuclei diffuse. Labeling with anti-H3S10f pericentrômeros occurred in the chromosomes and absent in interphase. The contributions of this work was to study the types of chromatin and its behavior in different stages of chromosome condensation, understand the karyotypic stability and small changes emanating from carioevolutivos events and cytogenetically characterize the species Manihot providing useful karyotypic parameters to the cytotaxonomic.