title: Variation of karyotype and nuclear DNA content among four species of Plectranthus L' Héritier, 1788 (Lamiaceae) from Brazil.
abstract: Plectranthus is a genus which includes species of ornamental and medicinal potential. It faces taxonomic problems due to aggregating species previously belonging to the genus Coleus, a fact that has contributed to the existence of various synonymies. The species Plectranthus amboinicus, Plectranthus barbatus, Plectranthus grandis and Plectranthus neochilus are included in this context. Some authors consider Plectranthus barbatus and Plectranthus grandis as synonyms. The present work was carried out with the aim of comparing plants of the above-mentioned species, originating from different localities in Brazil, with regards to chromosome number and karyotypic morphology, correlated to the nuclear DNA content. There was no variation in chromosome number among plants of the same species. Plectranthus amboinicus was the only species to exhibit 2n=34, whereas the others had 2n=30. No karyotypic differences were found among the plants of each species, except for Plectranthus barbatus. The plants of the Plectranthus species revealed little coincidence between chromosome pairs. The nuclear DNA content allowed grouping Plectranthus amboinicus and Plectranthus neochilus, with the highest mean values, and Plectranthus grandis and Plectranthus barbatus with the lowest ones. Differences in DNA amount among the plants were identified only for Plectranthus barbatus. These results allow the inference that the populations of Plectranthus amboinicus and Plectranthus neochilus present coincident karyotypes among their plants, and Plectranthus grandis is probably a synonym of Plectranthus barbatus.
authors.affiliation: Laboratory of Cytogenetics, Biology Department, Federal University of Lavras, Lavras-MG, PO Box 3037, Brazil.
authors.forename: Thaís Furtado
authors.initials: TF
authors.lastname: Nani
authors.affiliation: Laboratory of Biosystematics and Pollination, Plant Biology Department, University of Campinas, Campinas- SP, Monteiro Lobato Street, 255, Cidade Universitária Zeferino Vaz Barão Geraldo, Zip Code 13083-862, Brazil.
authors.forename: Amanda Teixeira
authors.initials: AT
authors.lastname: Mesquita
authors.affiliation: Laboratory of Cytogenetics, Biology Department, Federal University of Lavras, Lavras-MG, PO Box 3037, Brazil.
authors.forename: Fernanda de Oliveira
authors.initials: Fde O
authors.lastname: Bustamante
authors.affiliation: Laboratory of Environmental Biotechnology & Genotoxicity, Institute of Natural Sciences, Federal University of Alfenas, Alfenas-MG, Gabriel Monteiro da Silva Street, 700, Zip Code 37130-000, Brazil.
authors.forename: Sandro
authors.initials: S
authors.lastname: Barbosa
authors.affiliation: Laboratory of Environmental Biotechnology & Genotoxicity, Institute of Natural Sciences, Federal University of Alfenas, Alfenas-MG, Gabriel Monteiro da Silva Street, 700, Zip Code 37130-000, Brazil.
authors.forename: João Vítor Calvelli
authors.initials: JV
authors.lastname: Barbosa
authors.affiliation: Laboratory of Cytogenetics, Biology Department, Federal University of Lavras, Lavras-MG, PO Box 3037, Brazil.
authors.forename: Lisete Chamma
authors.initials: LC
authors.lastname: Davide
keywords: Cytogenetics; Cytotaxonomy; Flow cytometry; Karyotypic evolution