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A novel virus infecting yams (Dioscorea spp.), tentatively named “yam asymptomatic virus 1” (YaV1), was characterized and sequenced from an asymptomatic D. alata plant from Vanuatu. Sequence comparisons and phylogenetic analysis showed that YaV1 is a novel ampelovirus and has the smallest genome among “subgroup 1” members. RT-PCR-based screening of a yam germplasm collection conserved in Guadeloupe showed that YaV1 is prevalent in D. alata, D. bulbifera, D. cayen-nensis subsp. rotundata, D. esculenta and D. trifida accessions but causes no apparent symptoms. Additional phylogenetic analysis revealed a low variability of YaV1 in Guadeloupe in a limited part of the genome, and suggested the occurrence of plant-to-plant transmission.

Application web de gestion de données d'un Centre de ressources biologiques., DGIS permet de gérer les données des accessions de la collection d'ignames du CR Plantes Tropicales : données passeport, de taxonomie, de statut juridique, de modes de conservation, de campagnes de caractérisation, et des images.

Eight yam species (Dioscorea spp.) represented by 522 accessions (landraces and hybrids) were analysed for the individual sugars, catechins, phenolic acids and saponins contents of their tuber flours. Maltose, sucrose, glucose and fructose were quantified. Reducing sugars mean values were highly variable within species and ranged from 0.16%dry weight (DW) (SD ± 0.12) in D. dumetorum to 3.15%DW (±2.49) in D. esculenta. Maltose was detected only in D. esculenta. Chlorogenic acid, gallic acid and other phenolic acids ranged from 4.33 mg/g DW in D. bulbifera to 4.87 mg/g in D. alata and 9.55 mg/g in D. nummularia but were not detected in other species. Catechins (epicatechin and catechin) were highest in D. bulbifera bulbils (25.18 mg/g) and tubers (6.96 mg/g), and lowest in D. esculenta (0.32 mg/g). Their content is significantly correlated with dark flour colour and they most likely contribute to the oxidation of tuber flesh. Saponins (dioscin and gracillin) were quantified in only two species: D. cayenensis (5.94 mg/g, SD ± 3.78) and D. esculenta (3.74 mg/g, SD ± 3.72). Varietal selection may tend to reduce sugars levels and increase secondary metabolites with bioactive properties. HP-TLC is a suitable technique for the rapid quantification of compounds related to yam tuber flour quality.

Pour les Paimboa, les notions de temps et d’espace ne sont pas pensables séparées du tout de la société constituée des vivants et des morts. Aussi appréhendent-ils le temps d’abord dans le cadre des échéances rituelles d’un cycle socio-cosmique, notamment celles des funérailles qui consistent à faire converger le caractère imprévisible de la vie des humains et l’ordre régulièrement réaffirmé du cycle de l’igname. En cela, les vivants sont responsables de la transformation des morts en ancêtres, lesquels sont à leur tour garants de la croissance des ignames, leur principale culture vivrière. De même, l’espace est-il pensé en fonction de cette relation aux ancêtres et l’espace des vivants, celui des habitations, s’oppose à celui de l’inculte et de la forêt, là où sont conduits les morts. For the Paimboa people, notions of time and space have no meaning apart from society considered as a whole, including the living and the dead. Time is perceived through the ritual system of a socio-cosmic cycle; in other words, funerals become part of a process where the unpredictability of human life merges into the reasserted order of the yam cycle. Hence, the living, who depend on the yam as the main cultivated crop, are responsible for transforming the dead into ancestors who, in return, are responsible for the yam growth. Similarly, space has no reality apart from the relation with the ancestors. So, the space inhabited by the living, is in a distinctive opposition with the forest wilderness where the dead are driven to. Para los Paimboa, las nociones de tiempo y espacio no son concebibles fuera de la totalidad de la sociedad constituida por los vivos y muertos. Por lo tanto, conciben el tiempo principalmente en el marco de los plazos rituales de un ciclo socio-cosmico, especialmente los de los funerales que consisten en una convergencia de la impredecibilidad de la vida humana y del ciclo del ñame, regularmente reafirmado. A consequencia, los vivos son responsables de la transformación de los muertos en antepasados, a los cuales les toca a su vez garantizar el crecimiento del ñame, principal cultivo alimenticio. De la misma manera, el espacio se concibe en funcion de esta relación con los antepasados y el espacio de los vivos, o sea sus viviendas, se opone al espacio inculto, él de la selva donde se llevan los muertos.

Yam (Dioscorea rotundata Poir), is an important staple food and source of carbohydrate for developing country people, especially West Africa. Yam production is hampered by its inability to adequately control dormancy. The goal of this study is to investigate the molecular characteristic of dormancy. We performed a time course protein analysis and RNA fingerprinting at 0, 2, 4, 7, and 15 days by using Sodium Dodecyl Sulfate – Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Amplified Fragment Length Polymorphism (AFLP), respectively.Total RNA was isolated from dormant yam tubers incubated at 32°C ± 2C at relative humidity of 50% ± 5%. Complementary deoxyribonucleic acid (cDNA) generated from total RNA was subjected to AFLP techniques to identify differentially expressed genes up or down-regulated during dormancy.cDNA-AFLP results using different primer combinations revealed an array of transcript derived fragments (TDFs). About 14% of the TDFs were physiologically regulated either up or down or transiently induced, while 86% were expressed constitutively.Since variations in TDFs represent expression of developmentally regulated genes of interest, our results suggest that dormancy could be controlled through regulation of transcripts. This study may provide an avenue for the genetic manipulation of yam dormancy to preserve the organoleptic quality of yam and even its resistance to microorganisms., L’Igname, Dioscorea rotundata Poir, est un important aliment de base et une source de glucides pour les populations des pays en voie de développement, en particuliers l’Afrique de l’ouest. La production de l’igname est entravée par son incapacité de contrôler adéquatement sa dormance. L’objectif de cette étude est d’étudier les caractéristiques moléculaires de la dormance de l’igname. Une analyse des protéines et de l’ARN fingerprinting à des jours précis de 0, 2, 4, 7 et 15 jours à partir du début de l’expérience ont été donc effectués dans le temps en utilisant respectivement la méthode de l’électrophorèse sur gel de polyacrylamide (SDS-PAGE) et le polymorphisme de longueur de fragments amplifiés (AFLP).L’ARN total a été isolé à partir de tubercules d’igname dormants incubés à 32°C ± 2°C et à une humidité relative de 50% ± 5%. L'acide désoxyribonucléique complémentaire (ADNc) généré à partir de l'ARN total a été soumis à des techniques d’AFLP pour identifier l’expression induite des gènes différentiellement exprimés de manière accrue ou décroissante pendant la dormance.Les résultats d'ADNc-AFLP utilisant différentes combinaisons d'amorces primaires ont révélé des bandes de fragments dérivés transcrits (TDFs). Environ 14% des TDFs induits ont été physiologiquement régulés de manière accrue, décroissante ou transitoire, tandis que 86% exprimés sont des gènes constitutives.Puisque les variations des TDFs représentent l'expression de gènes d'intérêt dévelopementallement régulés, nos résultats suggèrent que la dormance pourrait être contrôlée par la régulation de ces transcrits. Cette étude donc peut fournir une avenue pour la manipulation génétique de la dormance de l'igname afin de préserver la qualité organoleptique de l’igname et même sa résistance aux microorganismes.

Wild yams (Dioscorea spp.) are medicinal plants rich in secondary metabolites of pharmacological interest, mostly allantoin and steroidal saponins. Their natural populations are overexploited and endangered. Cultivated yams could represent an alternative source of metabolites if interesting varieties could be selected. The objectives of the present study were to develop an HPTLC protocol for the simultaneous quantification of allantoin and steroidal saponins in dried yam powders, to compare species and varieties originating from distant geographical origins and to assess their potential as a source of secondary metabolites. Overall, 1151 accessions belonging to six cultivated species were analysed (1000 acc. from Nigeria, and 146 acc. from Vanuatu) and were compared to five commercial powders of wild yam (D. villosa). Allantoin, dioscin, gracillin, protodioscin, protogracillin and five unknown saponins were quantified. Dioscorea villosa powders varied in content and composition, with allantoin ranging from 0.23 to 22.35 mg/g (DW) and total saponins from 37.36 to 129.97 mg/g. Allantoin was present in the six species, with highest values in D. bulbifera bulbils (20.38 mg/g) and D. cayenensis tubers (17.12 mg/g). Steroidal saponins were quantified in three species, D. cayenensis, D. esculenta and D. rotundata, but were absent in D. alata, D. bulbifera and D. dumetorum. Mean total saponins contents were 42.15 mg/g in D. cayenensis, 17.65 mg/g in D. esculenta and 17/44 mg/g in D. rotundata, with accessions presenting very high values in D. cayenensis (78.31 mg/g) and D. rotundata (69.65 mg/g). For both allantoin and saponins, variation was observed within tubers and the tuber peel was richer than the flesh. Cultivated yam species represent a sustainable source of allantoin and steroidal saponins which could be further increased through conventional breeding.

Controlled pollinations were conducted to develop Dioscorea alata L. hybrids resistant to anthracnose (Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. Overall, 10,410 hand pollinations were carried out with Indian (IN) and Vanuatu (VU) clones in 53 different parental combinations, including diploids (2x) and tetraploids (4x) female and male plants. Pollination efficiency and seed set were comparable for IN2x × VU2x (54.6% and 23.0%) and IN2x × IN2x (57.4% and 28.9%). However, seedling survival with better resistance to anthracnose in nursery under natural disease pressure was higher for IN2x × IN2x (67.3%) compared to IN2x × VU2x (47.8%). IN2x female clones were crossed with VU2x and VU4x male clones in 12 parental combinations each. Pollination efficiency was higher for 2x parents (54.6%) compared to 4x parents (47.0%) but seed set (32.8%) and seedling survival (71.7%) were significantly higher for crosses between IN2x × VU4x. Overall, remarkable variation in pollination efficiency, seed set and seedling survival was observed between different parental combinations even when the same pollen parent was used. Interspecific hybridization between D. alata IN2x females and D. nummularia Lam. Vanuatu polyploid male was found to be successful with considerable variation in pollination efficiency, seed set and seedling survival (49.0, 20.8 and 35.3%). The hybrids exhibited intermediate characters between the two species with high tuber yield, anthracnose resistance but with fast tuber flesh oxidation. These results demonstrate the scope of polyploid and interspecific hybridization and the need for the international exchange of germplasm for D. alata genetic improvement.

Yam (Dioscorea rotundata Poir), is an important staple food and source of carbohydrate for developing country people, especially West Africa. Yam production is hampered by its inability to adequately control dormancy. The goal of this study is to investigate the molecular characteristic of dormancy. We performed a time course protein analysis and RNA fingerprinting at 0, 2, 4, 7, and 15 days by using Sodium Dodecyl Sulfate – Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Amplified Fragment Length Polymorphism (AFLP), respectively.Total RNA was isolated from dormant yam tubers incubated at 32°C ± 2C at relative humidity of 50% ± 5%. Complementary deoxyribonucleic acid (cDNA) generated from total RNA was subjected to AFLP techniques to identify differentially expressed genes up or down-regulated during dormancy.cDNA-AFLP results using different primer combinations revealed an array of transcript derived fragments (TDFs). About 14% of the TDFs were physiologically regulated either up or down or transiently induced, while 86% were expressed constitutively.Since variations in TDFs represent expression of developmentally regulated genes of interest, our results suggest that dormancy could be controlled through regulation of transcripts. This study may provide an avenue for the genetic manipulation of yam dormancy to preserve the organoleptic quality of yam and even its resistance to microorganisms., L’Igname, Dioscorea rotundata Poir, est un important aliment de base et une source de glucides pour les populations des pays en voie de développement, en particuliers l’Afrique de l’ouest. La production de l’igname est entravée par son incapacité de contrôler adéquatement sa dormance. L’objectif de cette étude est d’étudier les caractéristiques moléculaires de la dormance de l’igname. Une analyse des protéines et de l’ARN fingerprinting à des jours précis de 0, 2, 4, 7 et 15 jours à partir du début de l’expérience ont été donc effectués dans le temps en utilisant respectivement la méthode de l’électrophorèse sur gel de polyacrylamide (SDS-PAGE) et le polymorphisme de longueur de fragments amplifiés (AFLP).L’ARN total a été isolé à partir de tubercules d’igname dormants incubés à 32°C ± 2°C et à une humidité relative de 50% ± 5%. L'acide désoxyribonucléique complémentaire (ADNc) généré à partir de l'ARN total a été soumis à des techniques d’AFLP pour identifier l’expression induite des gènes différentiellement exprimés de manière accrue ou décroissante pendant la dormance.Les résultats d'ADNc-AFLP utilisant différentes combinaisons d'amorces primaires ont révélé des bandes de fragments dérivés transcrits (TDFs). Environ 14% des TDFs induits ont été physiologiquement régulés de manière accrue, décroissante ou transitoire, tandis que 86% exprimés sont des gènes constitutives.Puisque les variations des TDFs représentent l'expression de gènes d'intérêt dévelopementallement régulés, nos résultats suggèrent que la dormance pourrait être contrôlée par la régulation de ces transcrits. Cette étude donc peut fournir une avenue pour la manipulation génétique de la dormance de l'igname afin de préserver la qualité organoleptique de l’igname et même sa résistance aux microorganismes.

En élevage porcin, le Régumate, dérivé de synthèse de la progestérone, est utilisé dans le but de synchroniser les chaleurs des truies afin de les intégrer dans une bande. Cette technique est interdite en agriculture biologique. L’utilisation d’hormones exogènes est remise en question. Elle induit des problèmes environnementaux mais aussi sociétaux qui nécessitent une recherche d’alternatives. Par conséquent, des études sont menées. Au travers de l’expérimentation exploratoire “Synchronisation des truies à l’aide de phytoprogestagènes issues de l’igname jaune”, l’URZ (Unité de Recherches Zootechniques du centre INRA Antilles-Guyane) teste l’effet d’une ration enrichie en igname, plante cultivée en Guadeloupe, sur l’intervalle entre oestrus des cochettes. L’igname est pourvue d’une molécule ayant un effet progestagène, la diosgénine appartenant au sapogénine. L’étude s’effectue à l’aide de 9 cochettes de 6 mois de la PTEA et avec la variété d’igname D. cayenensis. A la fin de mon stage, l’expérimentation n'était pas finie. Dans l’attente des derniers résultats du terrain et ceux des analyses chimiques des prélèvements d’igname, une seule hypothèse peut être émise : le cycle des cochettes alimentées avec 1,5 kg d’igname pendant 18 jours n’a pas été modifié. Il est semblable au cycle dit “normal” des cochettes sans synchronisation, soit 21 jours entre deux oestrus. Aujourd’hui, l’hypothèse du potentiel effet progestagène de l’igname, c’est à dire sa capacité à agir sur la synchronisation des chaleurs chez les cochettes, n’est pas vérifié. En fonction des prochains résultats, cette expérimentation pourrait se poursuivre., In pig farming, the Regumate, a synthetic derivative of progesterone, is used to synchronize the heats of sows in order to integrate them into a band. This technique is prohibited in organic farming. The use of exogenous hormones is called into question. It induces environmental problems but societal as well, that require a research for alternatives. As a result, studies are conducted. Through the exploratory experiment "Synchronization of sows with phytoprogestagens derived help from yellow yam", the URZ (research unit of INRA Antilles-Guyana center) tests the effect of an enriched yam diet on the interval between oestrus at gilts. The yam contains a molecule with progestagenic effect, diosgenin belonging to sapogenin. The study is carrying out with nine 6-month-old gilts from PTEA and the variety D. cayenensis of yam. At the end of my internship, the experiment was not finished. Pending the latest field results and those of the chemical analyses of yam, only one hypothesis can be emitted: the cycle of gilts fed with 1,5 kg of yam for 18 days has not been modified. It is like “normal” cycle of gilts without synchronization, that is 21 days between two estrus. Today, the hypothesis of potential effect of yam, that is its capacity to act on the synchronization of heat in gilts, is not verified. Depending on the next results, this experiment could continue.

online en avril 2016; International audience; In West and Central Africa and in the Caribbean, yam is one of the most important sources of carbohydrates and has a great potential to improve food security. The yam production sector is, however, now challenged by the satisfaction of evolving consumers' preferences. Since little is known about consumers' preferences regarding yams' characteristics, product quality, and the drivers of yam purchase, six focus group discussions were conducted (for a total of 31 participants). Among the purchasing criteria, price was considered more important than the others. It was followed by the external damage, the origin, and the size of the tuber. The most frequently cited consumption criteria were the taste, the texture, and color of flesh after cooking. Taste was considered more important than the other criteria. Three consumers' profiles were established reflecting heterogeneity in preferences, especially as concerns the willingness to pay for yam and consumption habits. They were designated as the Hedonistic, the Thrifty and the Flexible. Our results suggest that innovations can be implemented to sustain and stimulate the development of the yam sector in Guadeloupe. Two main development paths were identified. The first path is the valorization of the great existing diversity of yam varieties and the increase in the level of information for consumers about product attributes such as the cooking mode, the origin, and the mode of production. Building a marketing strategy based on the valorization of this diversity can help maintain and preserve yam's agro-biodiversity and the satisfaction of rapidly evolving consumption habits. The second path is the definition of yam ideotypes that suit consumers' needs. We expect that tailoring the production to consumers' needs will have a positive impact on global food security in the Caribbean region.

International audience

International audience; Despite its importance regarding food security and household income, few studies have focused on yam (Dioscorea alata) crop physiology. Yet a better understanding of mechanisms and determinants of yield and quality production would enhance breeding programs capability to choose relevant key traits and develop high throughput methodologies to evaluate them. Based on recent results on yam interplant variability and competition we identify desirable key traits and implement phenotyping methods applicable within breeding programs. These phenotyping methods take advantage of increasing accessibility of sensor technologies and analysis methods. Our effort aimed at bringing those technologies into the field in order to capture highlighted yam heterogeneity and linked them with robust analysis methods allowing for high throughput phenotyping in tropical conditions. Finally, evaluation of on-field varietal performance are linked to ongoing research on identification and phenotyping of yam quality traits allowing us to study genotype by environment interaction on yam yield and quality.

This chapter shows how the transition of a linear innovation model to an iterative, participatory and ecological process has modified a technology and allowed it to be adopted. This case study is based on seed multiplication technology of yams in Haiti, the Miniset technology. We analyzed the development of this technique between 1990 and 2012, carrying out interviews with 26 experts (researchers, technicians, NGO leaders, farmers, etc.) and surveys of 106 farmers in three yam production regions of Haiti. We show how the failure of a linear technology model transfer allowed producers to improve this technique and how this and the greening of the technology paved the way for successful adoption of the technology. This success has been instrumental in increasing the production of yams in Haiti and producers' incomes.

Chlordecone, an organochlorine insecticide, continues to pollute soils in the French West Indies. The main source of human exposure to this pollutant is food. Root vegetables, which are staple foods in tropical regions, can be highly contaminated and are thus a very effective lever for action to reduce consumer exposure. We analyzed chlordecone contamination in three root vegetables, yam, dasheen and sweet potato, which are among the main sources of chlordecone exposure in food in the French West Indies. All soil types do not have the same potential for the contamination of root vegetables, allophanic andosols being two to ten times less contaminating than non-allophanic nitisols and ferralsols. This difference was only partially explained by the higher OC content in allophanic soils. Dasheen corms were shown to accumulate more chlordecone than yam and sweet potato tubers. The physiological nature of the root vegetable may explain this difference. Our results are in good agreement with the hypothesis that chlordecone uptake by root vegetables is based on passive and diffusive processes and limited by transport and dilution during growth.

This study aims to explore the potential of Dioscorea nummularia Lam. and to gather information as a prelude to its improvement by plant breeding. After a taxonomic clarification and a review of the botanical data, its geographical areas of origin and distribution are determined. A germplasm survey conducted on nine islands of Vanuatu enabled the collection of 110 accessions corresponding to 84 cultivars. These were grouped into: (1) wild forms under domestication, (2) annual types, (3) perennial-type cultivars of D. nummularia and (4) natural interspecific hybrids with D. alata L. Within each group, remarkable morphological variation exists for stem spininess, leaf shape, emerging leaf colour, tuber shape and tuber flesh colour. Selected accessions examined for ploidy had chromosome numbers ranging from 2n = 3x = 60 to 2n = 6x = 120. Chloroplast counts conducted on stomatal guard cells confirmed the variation in ploidy levels. Eight different male cultivars were studied for pollen fertility, but

RésuméAu Vanuatu, les jardins fournissent l'essentiel de la nourriture à 80% de la population. Mais ils sont aussi et surtout un lieu affectif où s'exprime une identité sociale. Une étude comparative menée sur deux groupes de même origine mais vivant, l'un en zone rurale (Mota Lava, îles Banks), l'autre en zone urbaine (Mango, île de Santo), montre que si des contraintes extérieures conditionnent l'organisation, la composition et l'utilisation de leurs jardins respectifs, ceux-ci continuent néanmoins à refléter les coutumes et les traditions de l'île d'origine de ces populations. AbstractUrban/rural Gardens in VanuatuIn Vanuatu, gardens produce most of the food for 80% of the population. But they are also a place to which feelings and a social identity are attached. A comparative study of two groups originally from the same island but now living respectively in rural (Mota Lava, Banks Islands) and urban (Mango, Santo Island) environments shows that, although outside factors condition their organization, layout and uses, gardens still reflect the customs and traditions of the island from which these groups came.þ

National audience; Loss of agrodiversity mediated by varietal legacy is an important concern, translating as crop species being at risk for genetic erosion, while loss of genetic resources may deplete material available for future breeding strategies. We explored varietal dynamics in the Guadeloupean agricultural yam system. Interviewing farmers about the varieties cultivated in the past compared to their current varieties demonstrated that no dramatic loss of varieties occurred in the two to three latest decades, and changes in variety frequency mostly affected former widespread varieties while frequency of uncommon varieties demonstrated some stability in cultivation frequency. Varietal dynamics nevertheless reflected strong sub-regional trends, and socio-economic impacts such as age of producers or farm levels of crop diversity.

National audience; Plant genetic resources are instrumental in the adaptation of agriculture to social and environmental change. They are the backbone of research and breeding programs aimed at the development and transfer of new crop varieties best suited to consumers’ needs and tastes and to new farming systems. To this aim, plant germplasm collections have been constituted worldwide. Securing such collections requires substantial human and financial investments that can prove difficult to maintain on the long run for small countries and territories such as most Caribbean countries. In Guadeloupe and Martinique, INRA and CIRAD have constituted large plant germplasm collections of tropical crops over several decades. They joined forces in 2010 to create the Tropical Plant Biological Resource Center of the French West Indies (CRB-PT), which is affiliated to both institutions. In this paper, we describe CRB-PT’s collections, services provided to end users and research programs as well as scientific and technical networking strategy.

DEUG; Au sein de l’Institut National de la Recherche Agronomique existe un Centre de Ressource Biologique des Plantes Tropicales (CRB-PT) qui conserve principalement des espèces cultivées, dont l’igname. La principale mission du CRB-PT est la diffusion aux agriculteurs ou aux centres de recherches de ces espèces. Cependant, l’igname est sujette à plusieurs types de virus ce qui empêche sa diffusion et son exportation. Pour pallier à ces problèmes, l’INRA a mis en place tout un système d’assainissement et de détection virale afin d’obtenir des plantes saines. Ces méthodes ont pour objectif d’assainir la collection d’ignames conservées in vitro. Cependant, ces techniques d’assainissement sont longues et fastidieuses et ne sont pas très efficaces car le taux d’assainissement n’est pas élevé. Pour autant, ces techniques de détection virale sont fiables et nécessaire à appliquer.

National audience; Cette communication a été réalisée dans le cadre des journées du RITA (Réseau d'Innovation et de Transfert Agricole) dédiées à la fertilisation des cultures tropicales, lesquelles ont regroupé des collègues des DOM français. Nous présentons les résultats obtenus en Guadeloupe sur la fertilisation minérale et organique de l'igname et nous les comparons à ceux reportés dans d'autres régions tropicales. Finalement, nous discutons de quelques facteurs et mécanismes qui pourraient expliquer la faible réponse de cette culture à la fertilisation.

Loss of agrodiversity mediated by varietal legacy is an important concern, translating as crop species being at risk for genetic erosion, while loss of genetic resources may deplete material available for future breeding strategies. We explored varietal dynamics in the Guadeloupean agricultural yam system. Interviewing farmers about the varieties cultivated in the past compared to their current varieties demonstrated that no dramatic loss of varieties occurred in the two to three latest decades, and changes in variety frequency mostly affected former widespread varieties while frequency of uncommon varieties demonstrated some stability in cultivation frequency. Varietal dynamics nevertheless reflected strong sub-regional trends, and socio-economic impacts such as age of producers or farm levels of crop diversity.

International audience

Depuis plusieurs années, des programmes de création de variétés d’ignames performantes, initiés à la demande des professionnels, ont abouti à la création de seize nouvelles variétés adaptées aux contraintes de production de Guadeloupe et conformes aux attentes des producteurs et des consommateurs. D'autres variétés sont attendues dans les années à venir. Ces dernières ont déjà été pré-évaluées en stations expérimentales et sont maintenant prêtes à être diffusées chez les producteurs. Plus récemment, de nouvelles variétés de madères ont été introduites en Guadeloupe afin de diversifier l’offre sur le territoire. Ces variétés, introduites sous formes de vitroplants sains, ont commencé à être multipliées pour être diffusées. Aujourd’hui, il est indispensable de multiplier, diffuser et promouvoir ces nouvelles variétés d’ignames et de madères auprès des agriculteurs, sous forme de matériel végétal de qualité. Pour y arriver, deux grands objectifs sont poursuivis dans le cadre de ce projet : i) Assurer la production et la diffusion de semences d’ignames de qualité. Ceci pourra être réalisé directement, ou par la mise en place d’un dispositif durable et économiquement viable, qui associe l’ensemble des acteurs de la filière. ii) Développer et promouvoir le portefeuille variétal. Pour cela, il est prévu de diffuser et caractériser ces nouvelles variétés dans les différentes zones de production, dans le cadre d’un réseau participatif. Ceci permettra d'accompagner les choix des producteurs, et de diffuser également des variétés traditionnelles, sous forte pression sanitaire, pour lesquelles l’accès aux semences par les professionnels est très limité. L’enjeu à moyen terme de ce projet est donc de mettre en place un dispositif de production de plants d’ignames et de madères de qualité en Guadeloupe, qui repose sur une forte implication des professionnels agricoles. Dans le même temps, le projet vise à accompagner le développement d’une structure locale de production de vitroplants de qualité, l’EARL CAVI.

Traditional yam-based cropping systems (shifting cultivation, slash-and-burn, and short fallow) often result in deforestation and soil nutrient depletion. The objective of this study was to determine the impact of yam-based systems with herbaceous legumes on dry matter (DM) production (tubers, shoots), nutrients removed and recycled, and the soil fertility changes. We compared smallholders’ traditional systems (1-year fallow ofAndropogon gayanus-yam rotation, maize-yam rotation) with yam-based systems integrated herbaceous legumes (Aeschynomene histrix/maize intercropping-yam rotation,Mucuna pruriens/maize intercropping-yam rotation). The experiment was conducted during the 2002 and 2004 cropping seasons with 32 farmers, eight in each site. For each of them, a randomized complete block design with four treatments and four replicates was carried out using a partial nested model with five factors: Year, Replicate, Farmer, Site, and Treatment. Analysis of variance (ANOVA) using the general linear model (GLM) procedure was applied to the dry matter (DM) production (tubers, shoots), nutrient contribution to the systems, and soil properties at depths 0–10 and 10–20 cm. DM removed and recycled, total N, P, and K recycled or removed, and soil chemical properties (SOM, N, P, K, and pH water) were significantly improved on yam-based systems with legumes in comparison with traditional systems.