The fragrant orchid Vanilla chamissonis: an appraisal of the genetic structure of wild populations from Osununú Natural Reserve, Misiones, ArgentinaResumen
Debido a diversos factores los cultivos comerciales de vainilla son altamente vulnerables a la erosión genética. Se ha demostrado que la especie Vanilla chamissonis produce compuestos bioeconómicos interesantes que podrían diversificar el mercado. En Argentina, la distribución de esta orquídea fragante se restringe a regiones específicas del noreste, como, por ejemplo, la Reserva Natural Osununú (San Ignacio, Misiones) donde crece de manera silvestre en sectores (núcleos). Este germoplasma, inexplorado, representa un endemismo localmente adaptado y, por lo tanto, es un recurso valioso que amerita preservarse. En este trabajo se llevó a cabo la caracterización genética de germoplasma de V. chamissonis. Además, se realizó la identificación molecular de los especímenes en un contexto filogenético empleando tanto marcadores nucleares como plastidiales. El genotipado expuso que, al menos, cuatro acervos genéticos contribuyen a la diversidad genética de estas plantas, y que ca. del 81% de la variación genética total se asigna dentro de las poblaciones. Los resultados actuales sugieren un predominio de la reproducción sexual, que el núcleo N1 emerge como una unidad candidata a conservarse, y la ocurrencia de una discontinuidad genética entre las poblaciones del noreste y del suroeste, que muestran constituciones genéticas diferentes. También se develó la ocurrencia de un tenue aislamiento por distancia. Nuestros resultados filogenéticos sugieren que es apropiado considerar al germoplasma estudiado como V. chamissonis. El conocimiento básico generado en este trabajo ayudará a guiar la iniciativa de manejo y conservación in situ, en curso en la reserva de Osununú.
Palabras clave: filogenética; genética poblacional; genotipado molecular; orquídeas silvestres; Osununú; provincia de Misiones
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Each nucleus’s relative gene pool composition is depicted in colored pie charts.The proportion of individuals assigned to each genetic cluster (DAPC clusters 1 to 4; see text) with a probability >0.90, is shown in blue, brown, orange, and red, respectively.The proportion of individuals with an ambiguous assignment (probability range: 0.483-0.815) is denoted in grey.
A. Scatterplot of the Discriminant Analysis of Principal Components (DAPC) depicting relative intra-group and among-group genetic distances.Dots represent individual samples; clusters are indicated with colors (blue: cluster 1, brown: cluster 2, orange: cluster 3, and red: cluster 4).Inset indicates the amount of variance in the grouping variable explained by the predictors in the discriminant function (discriminant analysis eigenvalues 72.38, 41.82, and 11.35, respectively).B. Genetic background of each individual surveyed.Each individual plant is represented by a vertical bar, which could appear partitioned into colored segments that represent the estimated membership probability to each of the four genetic clusters obtained (K=4).The colors are the same as in the scatterplot.
Numbers on branches represent bootstrap values (values >50% are shown).The colored tip of each branch designates the DAPC cluster to which the individual was assigned with a probability > 90% (blue: cluster 1, brown: cluster 2, orange: cluster 3, red: cluster 4).Individuals with ambiguous assignments are denoted by grey dots, while their estimated genetic constitution is visually represented by colored pie charts located on the side.Underlined individuals were used for sequencing (see text).
Southern, Central or Northern American species are denoted by purple branches, while blue branches indicate African or Asian species.Outgroup sequences are represented with black branches.Black dots mark the V. chamissonis individuals sequenced from the RNO, Argentina.Bootstrap support values > 60% are depicted above branches.The scale bar represents nucleotide substitutions per site.
Southern, Central or Northern American species are denoted by purple branches, whereas blue branches indicate African or Asian species.Outgroup sequences are represented with black branches.Black dots mark V. chamissonis individuals from RNO, Argentina, that were sequenced.Bootstrap support values > 60% are depicted above branches.The scale bar represents nucleotide substitutions per site.