Intraspecific variation of Vanilla planifolia (Orchidaceae) in the Huasteca region, San Luis Potosí, Mexico: morphometry of floral labellum

Vanilla planifolia is an orchid endemic to Mexico. It is important to characterize the morphological variation and to describe the morphological traits of its wild populations to enable use of this natural variation in agroecosystems and breeding programs. The objective of this study was to identify infraspecific morphological variation of V. planifolia in the San Luis Potosi Huasteca region, Mexico, where it is distributed naturally. We dissected 679 flowers from 40 accessions and subjected the labella to morphometric analysis, evaluating 76 morphological traits using an analysis of variance, principal component analysis, and cluster analysis. We found that there is highly significant variation among the accessions. The first three components explained 78% of the accumulated variance among groups. We identified four morphological groups, differentiated by the proximal lobe of the B region and the apical lobe of the F region, as well as the internal angles of the intermediate and lateral lobes of regions D and E. These angles determine labellum shape: rounded, bell-shaped, globular, or rhomboid. Morphotype I is oblanceolate shaped with tiny lobes. Morphotype II is bell-shaped, with long triangular lobes. Morphotype III is globular with large, wide lobes. Morphotype IV is rhomboid with very large lanceolate lobes. Morphological variation exists among V. planifolia specimens, which represent a strategic genetic resource in localities of San Luis Potosi, Mexico.