Is the quality of Kava (Piper methysticum Forst. f.) responsible for different geographical patterns ?

We argue that kava (Piper methysticum Forst. f.) is a Pacific domesticate that originated in Melanesia. We provide botanical, chemical, genetic and cultural evidence to suggest that farmers in the northern part of Vanuatu were the first to select the species as an asexually reproduced root crop. From Vanuatu, cultivars were carried eastward into Polynesia and westward into areas of New Guinea and Micronesia. Using herbarium data, isozyme and AFLP markers, we correlate the information gained from field surveys to HPLC analyses and attempt to demonstrate that chemotypes result from a selection process that is still active. The selection of particular mutants by farmers must have been. and still is, a rational process to preserve new characters when they appeared. Growers have selected cultivars to improve the chemical composition responsible for the physiological effects. Field experiments demonstrate that the chemotype is genetically controlled although the kavalactones content is determined by both genetics and environmental factors. The control and improvement of quality is therefore a cultural approach that aims at the identification of locations suitable for the cultivation of particular kava varieties. The appreciation of quality, appears to reflect the different cultures within Melanesia and between Micronesian, Polynesian and Melanesian consumers. Different ways of benefiting from the psychoactive properties of the plant explain the use of particular chemotypes and therefore the selection operated to preserve them. Clearly, the word kava refers to different beverages that produce different physiological effects according to what consumers desire. (Résumé d'auteur)