Résumé
Cacao (Theobroma cacao L.) was cultivated by the Mayas over two thousand years ago. The type of cacao cultivated by the Mayas is comprised within what is called the morphogeographic group Criollo, also known as Theobroma cacao L. sub sp. cacao. Criollo cacao was thought to originate in Central America and to have evolved independently from the cacao type originating from the Amazon basin. Morphological diversity and recent molecular analysis had supported this hypothesis. Cacao populations from the Amazon basin are included in the second morphogeographic group, which is called Forastero and is also considered as a different subspecies (sphaerocarpum), In order to gain a better understanding of the origin and the genetic basis of the cacao type cultivated in Central America, a study was carried out, using RFLP and microsatellite markers. For this study sampling and collection activities were performed in Venezuela, Colombia, Guatemala, Nicaragua and Mexico. In Mexico, samples were obtained from the Lacandona rainforest where wild Criollo trees have been reported and from archaeological sites. RFLP and microsatellite analyses revealed a significant low genetic diversity and a high level of homozygosity within the Criollo group. In contradiction to previous studies, "wild" and domesticated cacao from Central America were found to be genetically identical. Furthermore, Criollo individuals appeared to be closer to Colombian-Ecuadorian individuals than Colombian-Ecuadorian individuals were to Peruvian ones. In regard of our results, the hypothesis that Criollo and Forastero evolved independently into two different subspecies is not sustained. The results therefore suggest that the Criollo group probably originated from a few individuals in South America and that man participated in spreading of these individuals in Central America. (Résumé d'auteur)