Preliminary assessment of the degree of genetic diversity of Ecuadorean Ilex guayusa using inter simple sequence repeat (ISSR) markers

Abstract

The main objective of this study was to assess the degree of genetic diversity of llex guayusa; a species of ethnobotanic and commercial relevance for indigenous communities of the Ecuadorean Amazon. To this end, 157 individuals collected from small cultivation sites across six provinces were genetically characterized using nine Inter Simple Sequence Repeat (ISSR) markers. A total of 91 polymorphic bands were detected across the complete sample-set, but estimated heterozygosity (He = 0.19) revealed a reduced level of genetic variability for the species. Partitioning of genetic diversity (AMOVA) indicated that 82% of the variation observed for I. guayusa occurred within populations, and only 18% between populations. Accordingly, pairwise-Nei genetic distance indices (0.013 ≤ Ds ≤ 0.086) implied a reduced level of genetic divergence between individuals from different provinces. The low degree of genetic diversity found for I. guayusa could be ascribed to the fact that the species is exclusively cultivated via clonal propagation; a cultural activity which has probably homogenized the species"™ genetic pool across its geographic range. Notwithstanding, PCoA analysis could resolve collected germplasm into three distinct groups displaying a subtle genetic contrast in a directional gradient, from north to south. Certainly, the inclusion of a higher number of samples from underrepresented provinces (i.e. Sucumbíos), and wild populations would help resolve knowledge gaps regarding the genetic diversity and population structure of the species and its cultivation history in the region.