Comparative analysis of genetic variation in kava (Piper methysticum) assessed by SSR and DArT reveals zygotic foundation and clonal diversification.

Kava (Piper methysticum) is a major cash crop in the Pacific. The aim of this study was to assess genetic variation among 103 accessions of kava using SSRs and DArTs. Genetic structure was determined using clustering analyses (WPGMA) and principal coordinate analyses (PCA). Thirteen SSR primers and 75 DArT markers were found polymorphic, and the two types of markers generated similar clustering patterns. Genetic distances ranged from 0 to 0.65 with an average of 0.24 using SSRs and from 0 to 0.64 with an average of 0.24 using DArT. Eleven genotypes were identified with SSR while 28 genotypes were identified with DArT markers. By combining the two sets of markers, a total of only 30 distinct genotypes were observed. In the Vanuatu archipelago, noble cultivars originating from different islands clustered together within a very narrow genetic base despite their diversity of morphotypes. SSR and DArT fingerprints allowed the identification of kava cultivars unsuitable for consumption, so called two-days, and clearly differentiated the wild types classified as P. methysticum var. wichmannii from the cultivars as var. methysticum. Molecular data reveals that all noble cultivars evolved by the predominance of clonal selection. Although they are represented by clearly distinct morphotypes, these cultivars are genetically vulnerable and their potential to adapt to forthcoming changes is limited. These newly developed markers provide high resolution and will be useful for kava diversity analyses and quality assessment.

Re-introduction of kava (Piper methysticum) to the EU: is there a way forward?

Kava (Piper methysticum) is an effective anxiolytic that has been withdrawn from various consumer markets in European countries due to concerns over its hepatotoxicity. It is plausible that the reported hepatotoxicity may be due in part to plant substitution, or an incorrect cultivar, or plant parts being used (such as leaves or bark); thus both the plant chemotype and the plant part used may be critical factors. If re-institution of kava in the EU is to occur, more evidence is required to determine its safety and efficacy. Furthermore, according to current evidence, the study of traditional water soluble rhizome extracts using a noble cultivar of kava may be advised. The Kava Anxiety-Lowering Medication (KALM) project is due to start in late 2010 to address these considerations. The KALM project uses an aqueous rhizome extract of a noble cultivar of kava in participants with generalised anxiety and Generalised Anxiety Disorder (GAD). The project comprises of 1) an acute RCT, kava (180 mg of kavalactones) versus oxazepam and placebo in 20 anxious people, testing effects on cognition, mood, anxiety, and driving; 2) an 8-week RCT comparing kava (120 mg kavalactones) versus placebo in 100 patients with GAD. To assess differences between dosages, non-responders at 3 weeks will be titrated to 240 mg of kavalactones. The project will also assess the effects of kava on liver function tests and its side effects profile. A novel component of the project is the pharmacogenomic exploration of phenotypical responses (GABA system and cytochrome P450 markers). The results of the study may be of benefit to sufferers of anxiety and the future economy of the Pacific islands, potentially providing an important step in the way forward with kava.