Résumé
The chemical composition of 121 cultivars of
Piper methysticum originating from 51 Pacific islands, were investigated using HPLC. The results obtained for six major kavalactones (demethoxy-yangonin, dihydrokavain, yangonin, kavain, dihydromethysticin and methysticin) were submitted to cluster analysis and six distinct chemotypes were identified. Three field experiments demonstrated that chemotypes are not affected by environmental factors but are controlled genetically. Analysis of the isozyme variation for eight enzyme systems, revealed that these cultivars exhibited only three zymotypes. These are so similar that the differences in malate dihydrogenase and diaphorase could be explained as mutations. Few genes are thought to be responsible for the chemotype variation between cultivated clones. Because all cultivars are decaploids and sterile, it is suggested that mutagenesis might be used to induce genetic variability and to improve cultivar chemotypes.