ArgentinaCitogenetic analysis of Plectranthus barbatus Andrews naturalized in Tucumán province, Argentina

Abstract

The Brazilian boldo (Plectranthus barbatus Andrews) is a plant from India and naturalized in some regions of Argentina. It is used in folk medicine, pharmacology and as ornamental. The aim of this work was to characterize to P. barbatus by means of cytogenetics studies to contribute to the biological and genetics knowledge of the species. The material was collected in San Pedro de Colalao, Tucumán province, Argentina. Root-meristems (mitosis) and inflorescences (meiosis) were used for the cytological studies. To determine pollen viability of pollen mother cells the coloration technique of Blue Cotton in Lactophenol was employed. The chromosomal number in mitosis was 2n=32. In meiosis, monovalent and trivalent at Metaphase I, delayed at Anaphase I and Telophase I were observed. In pollen preparations a 70% of abnormal grains and a 30% of normal ones was found. According to the basic numbers of x = 6, 7 or 8 cited for the genus, it is deduced that it is a tetraploid species with irregular meiosis (autotetraploid). The failure in the seed formation explains its more frequent form of propagation: the vegetative multiplication. It would be convenient to keep into account this type of multiplication for maintaining a desired genotype, reaching genetics uniformity in the population at the same time that a quick obtaining of a great number of plants.