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Luganville, Vanuatu

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. Source

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. Source

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. Source

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. Source

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. Source

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