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

Abstract

Estudio preliminar de la diversidad genética de Ilex guayusa ecuatoriana mediante marcadores inter simple sequence repeat (ISSR) ResumenEvaluamos el grado de diversidad genética de Ilex guayusa, una especie de importancia etnobotánica y comercial para las comunidades indígenas de la Amazonía ecuatoriana. Caracterizamos genéticamente a 157 individuos, provenientes de chacras ubicadas a lo largo de seis provincias, con nueve marcadores ISSR (Inter Simple Sequence Repeats). Se detectó en total 91 bandas polimórficas, pero el índice de heterocigosidad estimada (H e =0.19) de la población reveló un nivel reducido de variabilidad genética para la especie. Los índices de distancias genéticas de Nei (0.013 ≤ Ds ≤ 0.086) revelaron un nivel reducido de divergencia genética entre individuos provenientes de provincias diferentes. De manera similar, el análisis de varianza molecular (AMOVA) demostró que solamente el 18% de la variación observada para I. guayusa ocurre entre poblaciones. El bajo grado de diversidad genética encontrado para I.guayusa puede ser atribuido al hecho de que esta especie es cultivada exclusivamente mediante propagación clonal; una actividad cultural que probablemente ha homogenizado el acervo genético de la especie a lo largo de su rango geográfico de cultivo. El análisis de coordenadas principales (PCoA) demostró que el germoplasma colectado puede estructurarse en tres grupos distintos caracterizados por un leve contraste genético en gradiente direccional, de norte a sur. La inclusión de un mayor número de muestras de provincias sub-representadas (ej. Sucumbíos) y poblaciones silvestres, si existen, ayudaría a esclarecer el nivel de diversidad genética y estructura poblacional de la especie, y la historia de su cultivo en la región.Palabras Clave. Aquifoliaceae, Guayusa, propagación clonal, baja diversidad genética. AbstractWe assessed the degree of genetic diversity of llex guayusa, a species of ethnobotanic and commercial relevance for indigenous communities of the Ecuadorian Amazon. We characterized 157 individuals, from small cultivation sites across six provinces, using nine Inter Simple Sequence Repeat (ISSR) markers. A total of 91 polymorphic bands were detected in, but estimated heterozygosity (He = 0.19) revealed a reduced level of genetic variability. Pairwise-Nei genetic distance indices (0.013 ≤ Ds ≤ 0.086) implied a reduced level of genetic divergence between individuals from different provinces. Accordingly, partitioning of genetic diversity (AMOVA) indicated that only 18% of variation observed for I. guayusa occurred between populations. 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 of cultivation. However, PCoA analysis resolved collected germplasm into three distinct groups displaying a subtle genetic contrast in a directional gradient, from north to south. The inclusion o...

Assessing the Genetic Diversity of Ilex guayusa Loes., a Medicinal Plant from the Ecuadorian Amazon

“…In this study, we found that I. guayusa presents a moderately low genetic diversity (He = 0.396) in the Ecuadorian Amazon region. In a previous report, we assessed the preliminary genetic diversity of guayusa from the Ecuadorian Amazon using ISSRs markers and found that it was considerably lower than the one found with SSR markers (He = 0.19) [25]. Direct comparisons are not possible since the molecular markers used were different; however, the higher levels of genetic diversity found could be attributed to the high discriminating power of SSRs [79][80][81].…”

“…[18], and I. aquifolium L. [19], among others [20][21][22], have been widely studied in terms of their genetic diversity and phytochemical composition [23,24]. In the case of guayusa, most research has focused on exploring its chemical properties and ethnobotanical uses [3,6,9], while information on genetics and cultivation history remains scarce [25]. Given that guayusa's primary strategy for reproduction is asexual and humanmediated, establishing its genetic status represents an interesting case study.…”

“…In order to understand which of these is the case of guayusa, in the present study we performed a preliminary assessment of the genetic diversity and population structure of 88 guayusa individuals from the Ecuadorian Amazon using 17 Simple Sequence Repeats (SSR) markers specific for I. guayusa. Having information of this species at the genetic level could contribute to establish conservation strategies and develop breeding programs [14] for the sustainable use of this agroforestry resource in a fragile and highly biodiverse region [25].…”