High-throughput analysis of flavokawains in Kava (Piper methysticum Forst. f.) roots, chips and powders and correlations with their acetonic extracts absorbance

Kava is a non-alcoholic beverage prepared by cold water extraction of the ground roots and stumps of Piper methysticum Forst. f. Kava contains flavokawains (FKs) which have been suspected of being potentially cytotoxic. Current HPLC protocols are not adapted to high-throughput quantification before export. The objectives of the present study were (i) to analyse with HPTLC the individual FKs in roots, stump, stems and peelings of four varieties grown in a controlled environment; (ii) to quantify FKs in 1053 commercial samples exported from Vanuatu in 2017-18-19 (370 roots, 381 chips and 302 powders) and (iii) to assess the efficiency of a colorimetric test for routine control. HPTLC plate scanning at 355 nm offered good linearity for three FKs with R2 > 0.99 and RSD 14 mg/g DW) were found in poor-quality varieties and in peelings unsuitable for consumption. Plant parts known for their good quality, such as roots and peeled stumps of noble varieties, presented low total FKs (< 7 mg/g). Great variation was observed in exported roots (2.53–24.56 mg/g), chips (2.73–18.03 mg/g) and powders (2.92–16.41 mg/g). HPTLC proved reproducible for the high-throughput quantification of FKs in kava. A positive relationship was confirmed between the absorbance of the acetonic extract and the total FKs (R2= 0.5211) (n = 1053). Multivariate analyses revealed that in roots, chips and powders, the three FKs are significantly correlated with high absorbance values. The absorbance of the acetonic extract gives a fair assessment of the FK content in kava products

Genome-wide genotyping elucidates the geographical diversification and dispersal of the polyploid and clonally propagated yam (Dioscorea alata)

International audienceBackground and Aims Inferring the diffusion history of many human-dispersed species is still not straightforward due to unresolved past human migrations. The centre of diversification and routes of migration of the autopolyploid and clonally propagated greater yam, Dioscorea alata, one of the oldest edible tubers, remain unclear. Here, we address yam demographic and dispersal history using a worldwide sample.Methods We characterized genome-wide patterns of genetic variation using genotyping by sequencing 643 greater yam accessions spanning four continents. First, we disentangled the polyploid and clonal components of yam diversity using allele frequency distribution and identity by descent approaches. We then addressed yam geographical origin and diffusion history with a model-based coalescent inferential approach.Key Results Diploid genotypes were more frequent than triploids and tetraploids worldwide. Genetic diversity was generally low and clonality appeared to be a main factor of diversification. The most likely evolutionary scenario supported an early divergence of mainland Southeast Asian and Pacific gene pools with continuous migration between them. The genetic make-up of triploids and tetraploids suggests that they have originated from these two regions before westward yam migration. The Indian Peninsula gene pool gave origin to the African gene pool. which was later introduced to the Caribbean region.Conclusions Our results arc congruent with the hypothesis of independent domestication origins of the two main Asian and Pacific gene pools. The low genetic diversity and high clonality observed suggest a strong domestication bottleneck followed by thousands of years of widespread vegetative propagation and polyploidization. Both processes reduced the extent of diversity available for breeding. and this is likely to threaten future adaptation