Cytogenetic and molecular characterization of three acesses of Lippia alba (Mill.) N.E. Br. (Verbenaceae). / CaracterizaÃÃo citogenÃtica e molecular de trÃs acessos de Lippia alba (Mill.) N.E.Br (Verbenaceae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

In Lippia alba (Mill.) NE Br. (Verbenaceae), commonly known as cidreira, chemotypes are observed and designated as La1-citral, La2-carvone and La3-linalool. They present morphological variation and different pharmacological activities. Morphologic, anatomical and phytochemical studies on these chemotypes has shown that, even under identical environmental conditions, those differences are noted. The species presents economical and medicinal importance, but the correct identification of those materials turn to be had because of such variations. Therefore it is necessary to adapt techniques that allow discrimination among the material. The aims of the present study are to verify, through cytogenetics and RAPD markers if the variations observed among those chemotypes happen due to genetic differences and to assist their correct identification and classification. Three accesses corresponding to the chemotypes La1, La2 and La3 were analyzed. For the study of the interphase nucleus and karyotype analysis, roots were pretreated with antimitotic agents and the slides were prepared by the cellular dissociation technique. For meiotic analysis, floral buds were collected, fixed and the slides prepared by the air drying technique. The pollen viability was evaluated by Alexander stain. In the analysis of RAPD, accomplished according to Williams et al. (1990), 47 primers were tested. The coefficients of similarity of Nei &Li (1979) were utilized for the construction of the distance matrix and dendrogram. La1 and La2 presented areticulate interphase nuclei, 2n=30 (6M + 9SM) and 2n=60 (15M+ 14SM + 1AC) and a total length of the genome of 43m and 83,67m, respectively. La3 was mixoploid with chromosome numbers varying between 2n=12 to 60 and one chromosome with characteristics of B- chromosome in some cells. Their interphase nucleus is a semi-reticulate type. The percentual of meiotic abnormalities was of 16,49%, 91,9% and 83,6% and the pollen viability, was of 82,35%, 52,51% and 34,75% for La1, La2 and La3, respectively. From the 47 tested primers, 70,2% were selected. 208 bands were amplified, 33 were monomorphic.Two main groups were formed, one with La1 individuals and other with La2, while La3 individuals were included in both groups. La3 presented larger variation inside (0,29) than the others (0,02 and 0,03 for La1 and La2, respectively). The variation observed among those chemotypes happen due to the existence of genetic differences among them. Our results allowed that La2- linalool is an autopolyploid of la1- citral. La3- carvone is possibly a hybrid resulting from the crossing between La1 and La2. It is possible that the changes observed constitute mechanisms that can lead to speciation of the chemotypes. Itâs necessary to gather those results, morphological, biochemical and ecological datas to review their taxonomic category.

ASSUNTO(S)

citogenÃtica citogen citologia vegetal lippia lippia planta medicinal. rapd rapd

ACESSO AO ARTIGO

Documentos Relacionados