Variation of karyotype and nuclear DNA content among four species of Plectranthus L' Héritier, 1788 (Lamiaceae) from Brazil.

Lisete Chamma Davide,João Vítor Calvelli Barbosa,Amanda Teixeira Mesquita,Fernanda De Oliveira Bustamante,Thaís Furtado Nani,Sandro Barbosa

doi:10.3897/compcytogen.v9i4.6255

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.

Highlights

The family Lamiaceae Martinov, 1820 contains approximately 250 genera and 6,500 species (Anon 2014)
Plants from Minas Gerais State were supplied by Medicinal Plant Garden of the University of Lavras (UFLA), the ones from Rio Grande do Sul State was provided by Medicinal Plant Garden of University of Santa Maria (UFSM) and plants from São Paulo State by the Campinas Agronomy Institute (IAC)
P. barbatus presented intraspecific variation: 8m+7sm, 9m+6sm and 10m+5sm, respectively corresponding to the specimens originated from the regions of Lavras/MG, Campinas/SP and Santa Maria/ RS (Table 2, Fig. 3)

Summary

Introduction

The family Lamiaceae Martinov, 1820 contains approximately 250 genera and 6,500 species (Anon 2014). Plectranthus L’ Héritier, 1788 is one of the most common genera of this family, and comprises about 300 species (Richardson 1992) that generally serve medicinal and ornamental interest (Thoppil 1993) Species of this genus are native to tropical and subtropical regions of Africa, Australia, the East Indies, the Malay Archipelago, and the Philipines (Lebowitz 1985). Coleus and Plectranthus have been considered distinct genera only because of morphological differences of the stamen; this characteristic has later been considered insufficient for the separation of these taxa This way, the Coleus species were aggregated to the genus Plectranthus, turning this grouping into a unique genus and independent of Ocimum Linnaeus, 1753 (Morton 1962). The taxonomic history of Plectranthus has contributed to some of its species being known by many different synonymies (Lukhoba et al 2006)

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Conclusion