Microsatellite Markers Confirm Self‐Pollination and Autogamy in Wild Populations of Vanilla mexicana Mill. (syn. V. inodora) (Orchidaceae) in the Island of Guadeloupe

Abstract

The study aimed at evaluating the mating system of Vanilla mexicana (Orchidaceae) in natural populations in the island of Guadeloupe. A total of 132 V. mexicana samples were collected from 12 sites in Guadeloupe (Basse-Terre). Five other samples coming from Martinique and Mexico completed our analyses. Reproductive biology experiments excluding pollinators with bagged flowers revealed 53.9% fruit set, a value identical to the natural fruit set measured in the populations. These results suggested that V. mexicana, unlike most Vanilla species, was reproducing by self‐pollination and autogamy. Due to lack of specific DNA markers for V. mexicana, microsatellite markers, previously developed in other Vanilla species, were used for the genetic analyses. Only 6 out of the 33 markers tested were transferable and polymorphic in V. mexicana. A panel of 51 V. mexicana samples genotyped with 3 polymorphic loci was finally retained for Guadeloupe population genetic analyses. A heterozygote deficiency was detected, and the selfing rate was estimated to 74%. These results confirmed the reproductive biology results as self‐pollination and autogamy were the most likely explanation for this deficit. Results were compared to those from allogamous wild Vanilla species and discussed in the light of suggested existence of a pollinator for V. mexicana in other areas (Mexico).