High-throughput sequencing of African chikanda cake highlights conservation challenges in orchids

Abstract

Chikanda is a traditional dish made with wild-harvested ground orchid tubers belonging to three orchidioid genera, Disa, Satyrium and Habenaria, all of which are CITES appendix II-listed. Identification of collected orchid tubers is very difficult and documentation of constituent species in prepared chikanda has hitherto been impossible. Here amplicon metabarcoding was used in samples of six prepared chikanda cakes to study genetic sequence diversity and species diversity in this product. Molecular operational taxonomic unit identification using similarity-matching reveals that species of all three genera were present in the chikanda samples studied. Disa was present in all of the samples, Satyrium in five out of six and Habenaria in one of the samples, as well as a number of other plants. The fact that each sample contained orchids and the presence of a wide variety of species from all genera in this traditional dish raise serious concerns about the sustainability of this trade and the future of wild orchid populations in the main harvest areas. This proof-of-concept study shows that Ion-Torrent PGM is a cost-effective scalable platform for metabarcoding using the relatively long nrITS1 and nrITS2 regions. 123Biodivers Conserv (2017) 26:2029-2046 DOI 10.1007/s10531-017-1343 Furthermore, nrITS metabarcoding can be successfully used for the detection of specific ingredients in a highly-processed food product at genus level, and this makes it a useful tool in the detection of possible conservation issues arising from commercialized trade or processed plant products.

Veronica officinalis Product Authentication Using DNA Metabarcoding and HPLC-MS Reveals Widespread Adulteration with Veronica chamaedrys

“…Our DNA metabarcoding results corroborate previous research that used metabarcoding to authenticate herbal products (Coghlan et al, 2012, 2015; Cheng et al, 2014; Ivanova et al, 2016; Veldman et al, 2017). In this study we confirm its applicability to test for presence of V. officinalis and simultaneously to detect substitution, adulteration and/or admixture of other Veronica species.…”

Phylogenomics and barcoding ofPanax: toward the identification of ginseng species

“…In DNA barcoding and plant product identification and authentication projects it is common to work with degraded DNA substrates for which it might be difficult to use methylation enrichment or the full plastid genome as a barcoding strategy. However, alternatives such as target enrichment and amplicon sequencing are possible [64, 123–125]. Here we have identified four variable regions that possess sufficient variation and genetic structure to discriminate most ginseng species.…”

Trade in Zambian Edible Orchids &ndash; DNA Barcoding Reveals Use of Unexpected Orchid Taxa for <em>Chikanda</em>

“…When we look at the chikanda type known as kapapa for example, SJK44 contains Platycoryne crocea, whereas SJK11, which is supposed to be a mix of kasebelela and kapapa, only seems to contain Satyrium species. In case of other chikanda types there seems to be more consistency: myala or real chikanda referred to Disa robusta, D. welwitschii and Satyrium buchananii, mshilamshila samples between fake chikanda samples as well [19]. It is well-known from literature that local species concepts are not necessarily congruent with scientific classifications and that species might be subject to overor underdifferentiation [50,51].…”

“…[12,13], whereas recently at least 32 species belonging to the genera Brachycorythis, Disa, Eulophia, Habenaria, Roeperocharis and Satyrium were suggested to be used for chikanda production based on collections in the field [12,[14][15][16][17][18][19] and one metabarcoding study of ready-made chikanda cakes [19]. To date, however, no study identified the orchids traded at the local markets, since the tubers lack sufficient morphological characters for taxonomic identification to species level [8,19]. Local classification systems categorize the tubers based on texture, harvesting locality, soil colour and phenology, but these are not likely to be congruent with scientific classifications [6,15].…”

“…DNA barcoding and metabarcoding has proven to be effective in the authentication of commercial wood species (Jiao, 2018), medicinal plants [21] and salep-producing orchids on Iranian markets [5]. The analysis of ingredients in Tanzanian chikanda cake with DNA metabarcoding revealed the presence of 21 different orchid species [19], but a DNA barcoding approach has not yet been applied to individual orchid tubers used to make this product. The aim of this study was to test to what extent species delimitation using standard molecular markers yields robust identification of chikanda orchid tubers traded on Zambian markets.…”