Morphological, phytochemical, and genetic variation in Hawaiian cultivars of 'awa (kava, Piper methysticum, Piperaceae)

Standardized morphological descriptions, quantitative phytochemical analyse s (HPLC) of major kavalactones and DNA finger printing (AFLP) were utilized to define the extent of variation existing between Hawaiian cultivars of P iper methysticum. For each cultivar, morphotypes and chemotypes were compar ed to their respective genotypes. Overall, 63 samples were analyzed for the ir kavalactone content and composition (44 root samples, 6 stump, 5 basal s tern, 7 leaves and 1 peelings). Results obtained from different cultivars p lanted in an homogeneous environment (soil and climate) are quite variable for the kavalactone content of their roots. Total kavalactone content decre ases when shade increases over the plants. Total kavalactone content marked ly increases with fertility, irrigation and in a cultivated type of habitat . However, kavalactone content appears to be independent of the age of the plant. For all cultivars analyzed, total kavalactone content decreases from the roots to the stump; the basal stems and the leaves exhibit the lower c oncentration. It is also observed that there is a correlation between the t otal kavalactone content and the size of the roots: smaller roots tend to h ave a higher kavalactone content. Feelings of the bark had a higher kavalac tone content than the stump and represent a very interesting by-product for the extraction industry. Chemotypes are similar in the roots and the stump , while they differ in the aerial parts where the concentrations in dihydro kavain and dihydromethysticin increase. DNA samples were extracted from fre sh leaves collected on 22 accessions. Most accessions, representing all Haw aiian morphotypes were monomorphs for the 21 pairs of primers assayed. Kava in Hawaii is a species with an extremely narrow genetic base. Morphologica l and phytochemical variation is obviously controlled by very few genes. Mo st cultivars representing different morphotypes are mast likely somatic mut ants from a common clonal source introduced by Polynesians during early set tlements.