The history of sweet potato in the Pacific has long been an enigma. Archaeological, linguistic, and ethnobotanical data suggest that prehistoric human-mediated dispersal events contributed to the ...distribution in Oceania of this American domesticate. According to the "tripartite hypothesis," sweet potato was introduced into Oceania from South America in pre-Columbian times and was then later newly introduced, and diffused widely across the Pacific, by Europeans via two historically documented routes from Mexico and the Caribbean. Although sweet potato is the most convincing example of putative pre-Columbian connections between human occupants of Polynesia and South America, the search for genetic evidence of pre-Columbian dispersal of sweet potato into Oceania has been inconclusive. Our study attempts to fill this gap. Using complementary sets of markers (chloroplast and nuclear microsatellites) and both modern and herbarium samples, we test the tripartite hypothesis. Our results provide strong support for prehistoric transfer(s) of sweet potato from South America (Peru-Ecuador region) into Polynesia. Our results also document a temporal shift in the pattern of distribution of genetic variation in sweet potato in Oceania. Later ^ introductions, accompanied by recombination between distinct sweet potato gene pools, have reshuffled the crop's initial genetic base, obscuring primary patterns of diffusion and, at the same time, giving rise to an impressive number of local variants. Moreover, our study shows that phenotypes, names, and neutral genes do not necessarily share completely parallel evolutionary histories. Multidisciplinary approaches, thus, appear necessary for accurate reconstruction of the intertwined histories of plants and humans.
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
R
2
> 0.99 and RSD < 3.0%. High total FKs (> 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 (
R
2
=
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.
Original multidisciplinary research hereby clarifies the complex geodomestication pathways that generated the vast range of banana cultivars (cvs). Genetic analyses identify the wild ancestors of ...modern-day cvs and elucidate several key stages of domestication for different cv groups. Archaeology and linguistics shed light on the historical roles of people in the movement and cultivation of bananas from New Guinea to West Africa during the Holocene. The historical reconstruction of domestication processes is essential for breeding programs seeking to diversify and improve banana cvs for the future.
Sweet potato (Ipomoea batatas (L.) Lam., Convolvulaceae) counts among the most widely cultivated staple crops worldwide, yet the origins of its domestication remain unclear. This hexaploid species ...could have had either an autopolyploid origin, from the diploid I. trifida, or an allopolyploid origin, involving genomes of I. trifida and I. triloba. We generated molecular genetic data for a broad sample of cultivated sweet potatoes and its diploid and polyploid wild relatives, for noncoding chloroplast and nuclear ITS sequences, and nuclear SSRs. Our data did not support an allopolyploid origin for I. batatas, nor any contribution of I. triloba in the genome of domesticated sweet potato. I. trifida and I. batatas are closely related although they do not share haplotypes. Our data support an autopolyploid origin of sweet potato from the ancestor it shares with I. trifida, which might be similar to currently observed tetraploid wild Ipomoea accessions. Two I. batatas chloroplast lineages were identified. They show more divergence with each other than either does with I. trifida. We thus propose that cultivated I. batatas have multiple origins, and evolved from at least two distinct autopolyploidization events in polymorphic wild populations of a single progenitor species. Secondary contact between sweet potatoes domesticated in Central America and in South America, from differentiated wild I. batatas populations, would have led to the introgression of chloroplast haplotypes of each lineage into nuclear backgrounds of the other, and to a reduced divergence between nuclear gene pools as compared with chloroplast haplotypes.
Yams (Dioscorea sp.) are staple food crops for millions of people in tropical and subtropical regions. Dioscorea alata, also known as greater yam, is one of the major cultivated species and most ...widely distributed throughout the tropics. Despite its economic and cultural importance, very little is known about its origin, diversity and genetics. As a consequence, breeding efforts for resistance to its main disease, anthracnose, have been fairly limited. The objective of this study was to contribute to the understanding of D. alata genetic diversity by genotyping 384 accessions from different geographical regions (South Pacific, Asia, Africa and the Caribbean), using 24 microsatellite markers. Diversity structuration was assessed via Principal Coordinate Analysis, UPGMA analysis and the Bayesian approach implemented in STRUCTURE. Our results revealed the existence of a wide genetic diversity and a significant structuring associated with geographic origin, ploidy levels and morpho-agronomic characteristics. Seventeen major groups of genetically close cultivars have been identified, including eleven groups of diploid cultivars, four groups of triploids and two groups of tetraploids. STRUCTURE revealed the existence of six populations in the diploid genetic pool and a few admixed cultivars. These results will be very useful for rationalizing D. alata genetic resources in breeding programs across different regions and for improving germplasm conservation methods.
•Contents of eleven crucial minerals were studied in four main parts of taro corms.•The upper part contained high levels of P, Mg, Zn, Fe, Mn, Cu and Cd.•The central part was characterised by high ...contents of K, P, Mg, Zn, Fe, Cu and Cd.•Ca was concentrated in the lower and the marginal parts.•The differences amongst genotypes (cultivars) were significant.
Taro (Colocasia esculenta) is an important root crop in the humid tropics and a valuable source of essential mineral nutrients. In the presented study, we compared the mineral compositions of four main parts of taro corm: the upper, marginal, central and lower (basal) parts. The freeze-dried taro samples were analysed for eleven minerals (K, P, Mg, Ca, Zn, Fe, Mn, Cu, Cd, Pb and Cr). The upper part, which plays a critical role in vegetative propagation based on headsets, contained high levels of P, Mg, Zn, Fe, Mn, Cu and Cd. The central part, which is essential for human nutrition, was characterised by higher concentrations of K, P, Mg, Zn, Fe, Cu and Cd. Ca was concentrated in the lower and marginal parts. The effect of the genotype was significant for more than half of the analysed minerals (i.e., Mg, Ca, Zn, Fe, Mn).
The selection of fine flavour cocoa and coffee varieties can lead to attractive niche markets but germplasm need to be analysed for non-volatile compounds and aroma precursors. In the present study, ...green beans of 202
Theobroma cacao
L. accessions (acc.), 64
Coffea arabica
L. acc., 35
C. canephora
Pierre ex A. Froehner, 7
C. arabusta
Capot & Aké Assi and 2
C. canephora
×
C. congensis
A. Froehner hybrids cultivated in Santo, Vanuatu, and harvested at full maturity, were analysed using High Performance Thin Layer Chromatography (HPTLC). In cocoa, 11 compounds were quantified: two alkaloids, two catechins, five proanthocyanidins, and two anthocyanins. Multivariate analyses revealed that Amenolado acc. are differentiated from Criollo, Forastero and Trinitario acc. due to their low caffeine, catechins, and proanthocyanidins contents. Hybrids involving an Amenolado parent also produce low non-volatile compounds contents. In coffee, 11 compounds were quantified: sucrose, two alkaloids, and eight chlorogenic acids. The two major species were differentiated by their mean caffeine content (12.69 mg/g in
C. arabica
vs. 16.04 mg/g in
C. canephora
), which is highly correlated with CGA and other chlorogenic acids. Each of the eight chlorogenic acids presented higher values in
C. canephora.
The ratio sucrose/alkaloids + chlorogenic acids was significantly higher in
C. arabica
(3.24) than in
C. canephora
(1.68) which could be an explanation for its comparative sweetness
. Coffea arabusta
interspecific hybrids presented an intermediate value (2.64). Congusta hybrids were low in sucrose. HPTLC is a cost-efficient technique when applied to germplasm characterization of non-volatile compounds in green cocoa and coffee beans. Chemotype selection appears promising for the development of fine flavor varieties.
ABSTRACT
Traditional agricultural systems have been a fundamental research focus of Pacific archaeologists for decades. In many island groups, it has been demonstrated that whole landscapes have been ...transformed to facilitate increased agricultural production. High‐resolution digital elevation models (DEM) derived from recent LiDAR survey data from Efate, Central Vanuatu, have now revealed that much of that island was completely modified by human activity prior to European contact. There are a range of substantial and more minor linear mound and circular features associated with agricultural development and innovation, of which researchers and contemporary populations are largely unaware. Detailed analysis of the features across one alluvial plain provides some quantification of the scale of landscape modification. These new data radically change perceptions of the Efate landscape and contribute to a range of debates including traditional Pacific Island food production, its surplus and sustainability, sociopolitical development, environmental change and depopulation.
RÉSUMÉ
Les systèmes traditionnels de culture horticoles en Océanie ont fait l'objet de recherches détaillées de la part des archéologues depuis des décennies. Dans plusieurs régions insulaires, il a été démontré que des paysages entiers avaient été transformés pour faciliter l'augmentation de la production agricole. Les modèles numériques de terrain à haute résolution, dérivés d'une récente couverture LiDAR sur l’île d’Efaté, Vanouatou central, révèlent que cette île était grandement modifiée par les activités anthropiques avant le premier contact avec les européens. On observe une série de billons linéaires imposants et d'autres secondaires, ainsi que des aménagements surélevés de formes circulaires qui révèlent un développement et une innovation agricoles, très peu connus des chercheurs et des populations actuelles. Une analyse détaillée de ces formes sur une plaine alluviale permet une première quantification de l'ampleur de la modification du paysage agraire. Ces nouvelles données changent radicalement notre perception des paysages d’Efaté et contribuent à alimenter le débat sur les systèmes de production alimentaire en Océanie, les surplus, le contexte socio‐politique, les changements environnementaux et la dépopulation.
To study the composition and amounts of phenolic compounds in ten tropical root crop species consumed daily worldwide and particularly in South Pacific, acidified aqueous extracts were analyzed. ...Among 134 samples, 78 components were found. Among total peaks detected from these fractions, 3 anthocyanins (peonidin-caffeoyl-feruloylsophoroside-5-glucoside, petunidin-3-glucoside and pelargonidin-3-glucoside), 5 flavonols (hyperoside, isorhamnetin-3-glucoside, kaempferol-3-glucoside, quercetin-3-glucopyranoside and quercetin-3′-glucoside,6′-acetate), 3 flavanols (catechin, epicatechin and epicatechin-3-gallate), and 3 phenolic acids (caffeic acid, chlorogenic acid and 3,5-dicaffeoylquinic acid) were tentatively identified by HPLC-DAD. Although many compounds remain to be identified, results suggest that these tropical root crops are good sources of anthocyanins and phenolic compounds. The greater yam (
Dioscorea alata) had the highest anthocyanin content (up to 93.3
mg CGE/100
g DW), while taro (
Colocasia esculenta) had the widest range of flavonols (up to 326.7
mg QGE/100
g DW). Cultivars of these staples should be exploited in breeding programs for the development of varieties with enhanced health and nutritional benefits.
Taro (Colocasia esculenta (L.) Schott) and sweet potato (Ipomoea batatas (L.) Lam.) are important food crops worldwide, whose productivity is threatened by climatic constraints, namely drought. Data ...calibration, validation, and model development of high-precision near-infrared spectroscopy (NIRS) involving multivariate analyses are needed for the fast prediction of the quality of tubers and shoots impacted by drought stress. The main objective of this study was to generate accurate NIRS models for quality assessment of taro and sweet potato accessions (acc.) subjected to water scarcity conditions. Seven taro and eight sweet potato acc. from diverse geographical origins were evaluated for nitrogen (N), protein (Pt), starch (St), total mineral (M), calcium oxalate (CaOx), carbon isotope discrimination (Δ13C), and nitrogen isotopic composition (δ15N). Models were developed separately for both crops underground and aboveground organs. N, Pt, St, and M models could be used as quality control constituents, with a determination coefficient of prediction (r2pred) between 0.856 and 0.995. δ13C, δ15N, and CaOx, with r2pred between 0.178 and 0.788, could be used as an informative germplasm screening tool. The approach used in the present study demonstrates NIRS’s potential for further research on crop quality under drought.
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