RAPD genetic diversity in cultivated vanilla:: Vanilla planifolia, and relationships with V-tahitensis and V-pompona

In Reunion Island (Indian Ocean) and other humid tropical areas, cultivated vanilla is represented mainly by the species Vanilla planifolia G. Jackson, syn. V.fragrans (Salisb.) Ames, indigenous to Mexico and Central America. Other cultivated species are V tahitensis J.W. Moore in South Pacific Islands and V. pompona Schiede in the West Indies. V pompona is naturally distributed in Central and South America, and the origin of 1 tahitensis is still questioned. The use of RAPD markers permitted to separate neatly individuals from the three species studied. Low levels of genetic diversity were detected in V planifolia in cultivation areas such as Reunion Island and Polynesia (Pacific Ocean), in accordance with the vegetative mode of dispersion of vanilla, and the history of recent introduction in these regions. Nevertheless, the occurrence of different introductions from which modern vanilla cultivars have evolved in these areas was demonstrated. Species-specific RAPD markers were selected and used successfully to analyse putative V planifolia x V tahitensis hybrid specimens. Within the sampling limit of the present study, it was also suggested that V tahitensis is probably not a species of direct hybrid origin (V planifolia x V pompona) but rather a species related to V. planifolia. These results are essential to guide further genetic analysis of cultivated vanilla specimens in introduction areas. (C) 2004 Elsevier Ireland Ltd. All rights reserved.