Luganville, Vanuatu
Luganville, Vanuatu
Time filter
Source Type

Taro [Colocasia esculenta (L.) Schott] is cultivated for its starchy corm consumed baked or boiled and processed in snacks (chips or French fries) to satisfy growing urban markets. Most consumers prefer non sweet taros. High content of sucrose (non-reducing sugar), glucose and fructose (reducing sugars) represent undesirable characteristics because they cause browning of the snacks. Breeding taro for improved corm quality is complex and phenotypic recurrent selection is impaired by the long growth cycle and the low vegetative propagation ratio. New high-throughput phenotyping tools are needed to select suitable hybrids in early clonal generations. The aim of the present study was to develop an HPTLC protocol for the quantitation of sugars in the fresh corm (FW). The individual sugars values in 60 hybrids released by four different breeding programs were compared with 300 cultivars from six different countries. Sucrose, glucose, fructose, maltose and ribose were quantitated. Mean total sugars varied from 1.83 to 6.28%FW in hybrids and from 1.32 to 7.69%FW in cultivars. The ratio sucrose/reducing sugars varied from 0.06 to 4.34 in hybrids and from 0.04 to 4.82 in cultivars. The protocol developed in this study is rapid, cost efficient, environment-friendly and more accurate than previous techniques based on dry matter because sample preparation is known to affect chemical composition of individual sugars. This technique can be used in taro breeding programmes for the early detection of undesirable hybrids with high levels of reducing sugars. © 2017, Springer Science+Business Media B.V.

Sardos J.,University of The Azores | Noyer J.-L.,CIRAD - Agricultural Research for Development | Malapa R.,VARTC | Bouchet S.,French National Institute for Agricultural Research | Lebot V.,CIRAD
Genetic Resources and Crop Evolution | Year: 2012

In Vanuatu, an oceanic archipelago located in south-west Pacific, taro (Colocasia esculenta (L.) Schott) is one of the staple crops. An eco-geographical survey of its genetic resources was conducted in ten villages, each located on a different island. A sample of 344 landraces referred as the National Sample (NS) was collected. Its genetic diversity was assessed using nine microsatellites markers and then was compared with an International Core Sample (ICS) that was previously distributed in the ten villages of the study in order to test the geographical distribution of allelic diversity as an effective mean for the on-farm conservation of root crops. The ICS was composed of 41 accessions, including 23 originating from South-East Asia. The molecular dataset revealed in the NS (1) 324 distinct multilocus genotypes, (2) six genetic clusters mainly differentiated by rare alleles, (3) a geographical structure of the genetic resources of taro based, within each village, on the dominance of one or two of these clusters rather that their exclusivity, and (4) an analogy between the patterns of dominant clusters between villages and the past and present social networks. In addition, accessions from the ICS revealed 52 new alleles. Based on these findings, we formulate hypotheses regarding the processes involved in the genetic diversification of taro in Vanuatu. We also discuss the use of this set of microsatellite markers along with the molecular dataset obtained from this study as effective tools to monitor the diversity and evolution of taro in the future. © 2011 Springer Science+Business Media B.V.

Lebot V.,CIRAD BIOS | Lawac F.,VARTC | Michalet S.,University Claude Bernard Lyon 1 | Legendre L.,University Claude Bernard Lyon 1
Plant Genetic Resources: Characterisation and Utilisation | Year: 2015

The starchy corms of taro (Colocasia esculenta) are consumed throughout the tropics and are essential for food security in many developing countries. Taro corms are increasingly processed into fries, chips, flours or flakes in urban areas, and varieties with attractive corm flesh colours are now needed. The identification of flavonoids in taro corms would add value to this crop. The present study developed a high-performance thin layer chromatography (HPTLC) protocol for the high-throughput screening of flavonoids in taro germplasm. Overall, 350 different accessions were analysed including 259 varieties from Vanuatu, one from Vietnam, eight from Thailand, eight from the Philippines, six from Malaysia, two from Japan and 18 from Indonesia. Forty-eight breeding lines (hybrids) including 21 from Vanuatu, 21 from Samoa, four from Hawaii and two from Papua New Guinea were also analysed. Ten flavones, namely luteolin-6-C-hexoside-8-C-pentoside, schaftoside, luteolin-3′,7-di-O-glucoside, homoorientin, isovitexin, orientin, luteolin-4′-O-glucoside, luteolin-7-O-glucoside, vitexin and apigenin-7-O-glucoside, were successfully detected in the corm and are responsible for the attractive yellow colour of the flesh and fibres. Quantitatively, luteolin-6-C-hexoside-8-C-pentoside and schaftoside were the most important of all the detected flavonoids. However, only 18% of the varieties analysed presented these two compounds and 80% presented poor flavonoid composition. No geographical structure of the variation was detected and the most flavone-rich varieties originated from Vanuatu, Thailand, the Philippines, Malaysia and Indonesia. The compounds detected in the present study were significantly and positively correlated, suggesting that there is potential for fast improvement through controlled crosses, subsequent evaluation of full-sib progenies and cloning of elite individuals. Copyright © NIAB 2015

PubMed | NARI Group, University of Ouagadougou, CTCRI, CIRAD and 8 more.
Type: Journal Article | Journal: PloS one | Year: 2016

Taro (Colocasia esculenta (L.) Schott) is widely distributed in tropical and sub-tropical areas. However, its origin, diversification and dispersal remain unclear. While taro genetic diversity has been documented at the country and regional levels in Asia and the Pacific, few reports are available from Americas and Africa where it has been introduced through human migrations. We used eleven microsatellite markers to investigate the diversity and diversification of taro accessions from nineteen countries in Asia, the Pacific, Africa and America. The highest genetic diversity and number of private alleles were observed in Asian accessions, mainly from India. While taro has been diversified in Asia and the Pacific mostly via sexual reproduction, clonal reproduction with mutation appeared predominant in African and American countries investigated. Bayesian clustering revealed a first genetic group of diploids from the Asia-Pacific region and to a second diploid-triploid group mainly from India. Admixed cultivars between the two genetic pools were also found. In West Africa, most cultivars were found to have originated from India. Only one multi-locus lineage was assigned to the Asian pool, while cultivars in Madagascar originated from India and Indonesia. The South African cultivars shared lineages with Japan. The Caribbean Islands cultivars were found to have originated from the Pacific, while in Costa Rica they were from India or admixed between Indian and Asian groups. Taro dispersal in the different areas of Africa and America is thus discussed in the light of available records of voyages and settlements.

Vandenbroucke H.,CIRAD - Agricultural Research for Development | Mournet P.,CIRAD - Agricultural Research for Development | Malapa R.,VARTC | Glaszmann J.-C.,CIRAD - Agricultural Research for Development | And 2 more authors.
Genome | Year: 2015

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. © 2015 Published by NRC Research Press.

Labouisse J.-P.,CIRAD - Agricultural Research for Development | Sileye T.,VARTC | Bonnot F.,CIRAD - Agricultural Research for Development | Baudouin L.,CIRAD - Agricultural Research for Development
Euphytica | Year: 2011

Coconut foliar decay (CFD) is a disease of coconut (Cocos nucifera L.) associated with infection by coconut foliar decay virus (CFDV), which is endemic in Vanuatu, South Pacific. The local cultivar 'Vanuatu Tall' (VTT) is the only cultivar that is fully tolerant to CFD, whereas introduced cultivars and hybrids are affected to different degrees. From 1967 to 2008 a conventional breeding programme was conducted with the aim of creating hybrid planting material combining tolerance to CFD with improved copra yield and high copra weight per nut. This objective was achieved by crossing the progeny of selfed trees of 'Rennell Island Tall' (RIT) cultivar, selected for their low susceptibility to CFD in field screening tests, with VTT, improved by mass selection and intercrossing. An improved VTT × RIT hybrid was identified with a high degree of tolerance to CFD (less than 1% of diseased trees after 11 years of exposure to high disease pressure). The annual production of the improved VTT × RIT hybrid ranged from 21. 9 to 28. 6 kg of copra per tree, depending on the RIT parent, and was, on average, 34% higher than that of 'VTT Elite' an advanced cultivar obtained after four selection cycles of local VTT. However, the production of the hybrid in Vanuatu involves constraints such as frequent replanting and isolation of the seed garden and CFD control for the RIT parents. The importance of conducting research on the genetic determinism and the mechanism of tolerance to CFD for better control of the disease in the event that it spreads outside Vanuatu is discussed. © 2010 Springer Science+Business Media B.V.

Chair H.,CIRAD - Agricultural Research for Development | Sardos J.,Bioversity International | Supply A.,CIRAD - Agricultural Research for Development | Mournet P.,CIRAD - Agricultural Research for Development | And 2 more authors.
Botanical Journal of the Linnean Society | Year: 2016

Phylogenetic relationships of Oceanian staple yams (species of Dioscorea section Enantiophyllum) were investigated using plastid trnL-F and rpl32-trnL( UAG ) sequences and nine nuclear co-dominant microsatellites. Analysis of herbarium specimens, used as taxonomic references, allowed the comparison with samples collected in the field. It appears that D. alata, D. transversa and D. hastifolia are closely related species. This study does not support a direct ancestry from D. nummularia to D. alata as previously hypothesized. The dichotomy in D. nummularia previously described by farmers in semi-perennial and annual types was reflected by molecular markers, but the genetic structure of D. nummularia appears more complex. Dioscorea nummularia displayed two haplotypes, each corresponding to a different genetic group. One, including a D. nummularia voucher from New Guinea, is closer to D. tranversa, D. alata and D. hastifolia and encompasses only semi-perennial types. The second group is composed of semi-perennial and annual yams. However, some of these annual yams also displayed D. alata haplotypes. Nuclear markers revealed that some annual yams shared alleles with D. alata and semi-perennial D. nummularia, suggesting a hybrid origin, which may explain their intermediate morphotypes and the difficulty met in classifying them. © 2016 The Linnean Society of London.

Blanco J.,IRD Montpellier | Pascal L.,UMII | Ramon L.,VARTC | Vandenbroucke H.,CIRAD - Agricultural Research for Development | Carriere S.M.,IRD Montpellier
Agriculture, Ecosystems and Environment | Year: 2013

Shifting cultivation is considered to be the most widespread cultivation system in the tropics. However, it remains poorly understood in some countries. The measurement of agrobiodiversity in these systems, which could be used to better understand its sustainability in the face of social, economic and environmental change, has been the focus of little research. This study aimed to measure the agrobiodiversity on small, family-farmed, shifting cultivation fields in Vanuatu and to test the effect of different demographic pressures, locations and cropping systems. A total of 297 fields in 6 villages were measured and a spatial approach was used for comparisons at the field, farmer and village scales. Shifting cultivation in Vanuatu includes three main cropping systems, based on yams, rain-fed taro or irrigated taro, and other subsidiary systems. The configuration of each farm's cropping system depends on each farmer's choices and opportunities. Agrobiodiversity in fields was high with a mean species richness of 10.2 (±4.8. SD) and an intraspecific richness of 8.6 (±7.3. SD). In a crop sequence, agrobiodiversity decreased for yam and rain-fed taro fields but this decrease was faster in yam fields. Cluster analyses showed that the main factor influencing agrobiodiversity at the field and farmer scale was the cropping system. At the village scale, however, the cropping system only appeared to influence intraspecific richness as no difference in species richness was found between villages. Moreover, ANOVA showed no village effect on agrobiodiversity, which raises the question of whether there is an effect of scale affecting biodiversity assessments in landscapes. No correlation was found between agrobiodiversity and demographic pressures or fallow length at any spatial scale. This study showed that the agrobiodiversity is variable at the field and farmer scale but is stable across villages and islands and is influenced only by the dominant cropping system. It suggests that this system is still resilient in the face of recent economic, social and environmental changes, but requires further multiple scale studies for a deeper understanding. © 2013 Elsevier B.V.

Lebot V.,CIRAD AGAP | Malapa R.,VARTC | Jung M.,ISTOM
New Zealand Journal of Crop and Horticultural Science | Year: 2013

The objective of the present study was to test the robustness of near infrared spectroscopy (NIRS) for the prediction of total N content in underground storage organs across a diverse range of root and tuber crop varieties. Overall, 1096 accessions (acc.) from five different species (cassava = 112 acc., cocoyam =117 acc., sweet potato = 225 acc., taro = 306 acc. and yams = 266 acc.) were chemically analysed for total N and minerals, as well as starch, sugars and cellulose. For validation of the models, 178 samples composed of the same five different species were collected in farmers fields, at random. All spectra were taken over the wavelength range of 350-2500 nm. Partial least-squares (PLS1) regression technique was used to develop predictive models. Their comparison with the chemical values allowed the establishment of equations of calibration. In terms of predictive performance, the equation for total N should be considered as very good with a r 2 pred of 0.93 (SEP = 0.87). Minerals presented low r 2 pred of 0.62 (SEP = 1.05). Starch and sugars presented r 2 pred of 0.77 and 0.86, respectively (SEP = 3.2 and 1.82). Cellulose could not be satisfactorily predicted with a low r 2cv (0.57) for the calibration. The r 2 pred values of total N, starch and sugars are high enough to allow good estimates of their contents, confirming the interest of NIRS for predicting rapidly these major compounds. Potential applications are discussed. © 2013 The Royal Society of New Zealand.

Lebot V.,CIRAD | Malapa R.,VARTC | Sardos J.,Bioversity International
Genetic Resources and Crop Evolution | Year: 2015

Cassava (Manihot esculenta Crantz) was introduced into Vanuatu shortly after 1850. Farmers have since selected and clonally propagated volunteer seedlings and new morphological variants found in cultivated plots. As cassava is free of serious pests and diseases in Vanuatu, it is unknown what are the farmers’ sought traits leading to diversification. The aim of the present study is to investigate the diversification process and to identify the cultural factors that contribute to shape cassava diversity in Vanuatu. We characterized morphologically, using twelve descriptors, and chemically (dry matter, starch, sugars, proteins, cellulose, minerals), the national germplasm collection composed of 145 landraces collected from eleven different islands. Farmers’ traditional knowledge on landraces was documented in ten villages, each located on a different island. A wide morphological variation was found among the accessions with few duplicates, the number of distinct morphotypes is 141. However, the sampling strategy most likely underestimated the total number of existing landraces. Cluster analysis revealed no geographical structuring among morphological groups, confirming the wide movement of germplasm between islands across the archipelago. Dry matter (DM) and starch are the least variable compounds with CV % of respectively 12.3 and 3.4 %; these two traits being highly correlated. Sugars (CV 42 %), cellulose (30.3 %), proteins (34.4 %) and total minerals (17.4 %) are more variable. The human selection pressure is focusing on good quality landraces based on high DM and starch contents, with different farmers in different islands focusing independently on the same traits. Implications for germplasm conservation and use strategies are discussed. © 2014, Springer Science+Business Media Dordrecht.

Loading VARTC collaborators
Loading VARTC collaborators