The fragrant orchid Vanilla chamissonis: an appraisal of the genetic structure of wild populations from Osununú Natural Reserve, Misiones, ArgentinaAbstract
The commercial crops of vanilla face a significant risk of genetic erosion due to various factors. Vanilla chamissonis, a species with promising bioeconomic compounds, is found in limited regions in Argentina, particularly in the Osununú Natural Reserve in San Ignacio, Misiones, where it grows wildly in sectors (nuclei). This locally adapted germplasm of V. chamissonis holds considerable value and needs preservation efforts. In this study, we genetically characterized unexplored V. chamissonis germplasm and identified specimens within a phylogenetic framework using nuclear and plastid markers. The genotyping revealed that at least four gene pools contribute to the genetic diversity of these plants, with approximately 81% of total genetic variation allocated within populations. Sexual reproduction seems to predominate, and population N1 is a candidate for conservation. There is a genetic discontinuity between northeastern and southwestern nuclei, due to their different genetic constitutions and the tenuous isolation by distance. Phylogenetic results confirm the surveyed vanilla germplasm as V. chamissonis. This research provides essential insights for guiding the ongoing conservation and management efforts at the Osununú Reserve.
Keywords: molecular genotyping; Misiones province; Osununú; phylogenetics; population genetics; wild orchids
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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.