Caracterización molecular de algunas especies y variedades de ñame presentes en la Costa Atlántica colombiana

Molecular characterisation of some species and varieties of yam present on the Colombian Atlantic Coast

En Colombia el ñame (Dioscorea data y Dioscorea rotundata) es un cultivo de importancia para los pequeños productores de la Costa Atlántica. El Programa Colombiano de Biotecnología Agrícola (PBA) de Ñame tiene el objetivo de incrementar la sostenibilidad de grupos de campesinos de la región, adelantando investigaciones participativas en diferentes aspectos relacionados con el cultivo. En el presente trabajo, el objetivo principal fue caracterizar molecularmente las ocho variedades de ñame utilizadas en el PBA, a través de marcadores moleculares tipo AFLP para determinar si existe concordancia entre la taxonomía morfológica establecida para la clasificación de las especies y variedades con la discriminación y agrupación de los individuos por sus perfiles de bandas moleculares aportados por los AFLP Para la obtención de los patrones de AFLP se utilizaron los kits de Gibco-BRL, New York Analysis System I y Analysis System II, siguiendo los manuales de instrucción. Para el análisis estadístico se realizaron matrices de presencia ausencia, se determinaron las similitudes a partir del índice de similaridad de Dice con el paquete estadístico Gel Stats. Posteriormente, las matrices se transformaron en matrices de distancia, y a partir de éstas se construyeron los dendogramas utilizando como estrategia de agrupamientos UPGMA (Unweighted Pare Group Method Averange). Finalmente se realizó una comparación entre matrices utilizando el análisis de permutaciones de Mantel. Los resultados muestran que de las siete variedades de Dioscorea alata analizadas solamente tres de ellas presentan polimorfismos que permiten diferenciarlas. Las otras cuatro se agruparon como una sola variedad. 

Seven varieties of the Dioscorea alata specie (but only one variety of the Dioscorea rotundata specie) have been morphologically characterised in Colombia. These varieties have been used in the Colombian Yam Agricultural Biotechnology Programme (ABP) to increase the sustainability of groups of poor rural workers from the Colombian Atlantic Coast by providing them with plants having good organoleptic characteristics and increased tuber yield. This work's main objective was the molecular characterisation of those varieties of yam from the Colombian Atlantic Coast used in the ABP, through Amplified Fragment Length Polymorphism (AFLP) molecular markers. This aimed at determining if there is conformity between that morphological taxonomy established for the classification of ABP programme species and varieties with the discrimination and grouping of individuals by their molecular band profiles provided by AFLP Seven varieties of D. alata specie and the sole variety of the D. rotundata specie were characterised. Gibco-BRL, New York Analysis System I and Analysis System II kits were used to obtain AFLP patterns, following handbook instructions. Presence/absence matrices were constructed for the statistical analysis; similarity was determined from the Dice similarity index by using the Gel Stats statistical package. Later matrices became distance matrices and dendograms were constructed from these by using UPGMA (Unweighted Pair Group Method Average) for grouping strategy. Comparison was then made between matrices by using Mantel permutation analysis. The results show that only three of all the seven Dioscorea alata varieties analysed presented polymorphism allowing them to be differentiated. The other four varieties were grouped as a sole variety or belonged to a single variety. These results have great importance for widening information concerning yam in Colombia, particularly for the Colombian ABR since it makes it possible to reduce collection and maintenance costs, leading to information regarding each accession to Colombia's germplasm banks to be increased. This is the first molecular characterisation work carried out in Colombia on yam species (Dioscorea spp.).