Geographic survey of genetic variation in Kava (Piper methysticum Forst. f and P. wichmannii C. DC.)

A survey of the genetic resources of kava (Piper methysticum Forst. f. and P. wichmannii C. DC.) was conducted throughout the Pacific. Leaf tissues of more than 300 accessions, collected on 35 islands, were analyzed for isozyme variation in eight enzyme systems including ACO, ALD, DIA, IDH, MDH, ME, PGI, and PGM. Isozymes in P. methysticum cultivars from Polynesia and Micronesia were monomorphic for all enzyme systems examined; however, cultivars from Melanesia were polymorphic for ACO, DIA, MDH, and PGM. The genetic base of this crop is much narrower than previous morphological and biochemical studies suggest. Most of the morphotypes and chemotypes apparently originated through human selection and preservation of somatic mutations in a small number of original clones. Isozymes of P. wichmannii confirmed its status as the wild progenitor of kava. Piper methysticum cultivars and P. wichmannii and P. gibbilimbum C. DC. wild forms were all found to be decaploids with 2n = 10x = 130 chromosomes, but there was no firm evidence that interspecific hybridization has played a role in the origin of P. methysticum. (Résumé d'auteur