Resumen de Genetic structure and chemical diversity of the aromatic shrub Lippia origanoides H.B.K. (Verbenaceae) in two populations from northern Colombia

Nelson Enrique Vega Vela, Wilman A. Delgado, Maria Isabel Chacon Sánchez

• Lippia origanoides, H.B.K., is an aromatic shrub of the Verbenaceae family characterized by the great potential of its essential oils in several industries. However, very little is known about basic biological aspects such as genetic structure and chemical diversity. L. origanoides is mainly distributed in xerophytic and subxerophytic areas in northern South America. In Colombia it occurs in semiarid areas of the north, northeast and southwest of the country. In the present study, the chemical diversity and genetic structure of two populations of L. origanoides from Colombia, one from the department of Magdalena in the Atlantic coast in the north, and the other one in the Canyon of the Chicamocha river in the northeast, were compared. Individuals were sampled in each of the two populations and ISSR and AFLP molecular markers were applied to document the distribution of the genetic diversity within and among populations. Essential oils were extracted by steam distillation from individuals collected in the two populations and analyzed by gas chromatography and mass spectrometry (GC-MS). The results suggest that genetic diversity levels of L. origanoides in Magdalena and Chicamocha are relatively high (Hs ranges from 0.35 to 0.37) and comparable to other allogamous plant species and to other related species of the same genus. A low genetic differentiation was found among the two populations, in spite the relatively large geographical distance among them. The essential oils of L. origanoides can be classified as monoterpenic type, however, according to the relative amount of the major compound, six different kinds of essential oils are proposed. Four of them (A, B, C, D and E) are present in the Chicamocha canyon, while two of them (A and F) are present in Magdalena. In summary, the essential oils from individuals collected in the Canyon of the Chicamocha river are rich in thymol and carvacrol, while those from Magdalena are rich in thymol and with relatively high contents of Eucalyptol and α- Phelandren. These results suggest an important presence of genetic and chemical diversity in this species, which should be more deeply studied in order to make a more efficient use of this promising plant resource.