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1. Fine-scale tracking with passive acoustic telemetry can yield great insights into the movement ecology of aquatic animals. To predict fine-scale positions of tagged animals in continuous space from spatially discrete detection data, state-space modelling through the R package YAPS provides a promising alternative to frequently used positioning algorithms. However, YAPS cannot currently classify multiple kinds of movement that may be used as proxies for individual behaviours of study animals (behavioural states), an endeavour that is of increasing interest to movement ecologists.2. We advance YAPS by incorporating the functionality to predict behavioural states by using an iterative maximization framework. Our model, which we call YAMS, occurs in continuous-time and therefore we adapt current HMM machinery to accommodate this while remaining within a likelihood framework that provides rapid fitting. We test our model using simulations and approximately six days worth of Northern pike data from Hald Lake, Denmark.3. YAMS is shown to produce accurate parameter estimates and random effect predictions when model results were compared to simulated data, with behavioural state accuracies of 0.94 and 0.79 for two- and three-state models, respectively, and location state root mean squared errors of 1.8 m for both models. In addition, the behavioural states are shown to reflect varying speeds of the pike, yielding a highly interpretable classification.4. This research has the potential to be broadly applicable to both ecologists interested in identifying fine scale space use and behavioural states from acoustic telemetry data, as well as to statisticians who may wish to use standard HMM machinery to fit continuous-time HMMs to animal movement data.

Background and aims. Among the numerous pantropical species of the yam genus, Dioscorea, only a small group occurs in the Mediterranean basin, including two narrow Pyrenean endemics (Borderea clade), and two Mediterranean-wide species (D. communis and D. orientalis, Tamus clade). However, several currently unrecognized species and infraspecific taxa have been described in the Tamus clade due to significant morphological variation associated with D. communis. Our overarching aim was to investigate taxon delimitation in the Tamus clade using an integrative approach combining phylogenomic, spatial and morphological data. Methods. We analysed 76 herbarium samples using Hyb-Seq genomic capture to sequence 260 low-copy nuclear genes and plastomes, together with morphometric and environmental modelling approaches. Key results. Phylogenomic reconstructions confirmed that the two previously accepted species of the Tamus clade, D. communis and D. orientalis, are monophyletic and form sister clades. Three subclades showing distinctive geographic patters were identified within D. communis. These subclades were also identifiable from morphometric and climatic data, and introgression patterns were inferred between subclades in the eastern part of the distribution of D. communis. Conclusions. We propose a taxonomy that maintains D. orientalis, endemic to the eastern Mediterranean region, and splits D. communissensu lato into three species: D. edulis, endemic to Macaronesia (Canary Islands and Madeira); D. cretica, endemic to the eastern Mediterranean region; and D. communissensu stricto, widespread across western and central Europe. Introgression inferred between D. communis s.s. and D. cretica is likely to be explained by their relatively recent speciation at the end of the Miocene, disjunct isolation in eastern and western Mediterranean glacial refugia and a subsequent westward recolonization of D. communis s.s. Our study shows that the use of integrated genomic, spatial and morphological approaches allows a more robust definition of species boundaries and the identification of species that previous systematic studies failed to uncover.

The present study described fifteen (15) cultivars of yams of the varietal group "Pémonon" cultivated in Burkina Faso. Twenty-seven (27) qualitative characters, ten (10) from the stems, nine (9) from the leaves, five (5) from the tubers and three (3) from the flowers were used to characterize the collection. The expeimental design was Randomized Complete Block Design replicated three times. The experiment was carried out during 2019-2020 and 2020-2021 seasons at the village of Onliassan, in the province of Sissili. The study showed a large phenotypical diversity. These collected qualitative data allowed to classify these cultivars into the complex ofD. cayeninsis-rotundataspecies and to identify new nine (9) cultivars.

Gulf of Guinea (GoG) member nations that signed the Yaoundé Architecture for Maritime Security (YAMS) in June 2013 must work together to combat piracy and other maritime crimes. Despite international backing for this initiative, maritime security challenges have grown. In the GoG, seafarers are abducted, tortured, and ransomed more often than elsewhere. The regional response to maritime security issues in the GoG has not been effective because of several factors, including the cooperation’s non-binding code of conduct, the insufficient implementation and operationalization of YAMS owing to its cumbersome design, and the member states’ different interests and limited capacities to support their own maritime security. Drawing on open-source literature, including academic research, newspaper articles, and government reports, this study examines these factors that have hindered swift and effective implementation of YAMS. Through case studies of select member states, the thesis argues that these GoG nations with land-based security challenges must not only direct more resources to their respective navies but also collaborate to enhance YAMS. Piracy knows no borders, and thus, it requires a collective response. The thesis recommends GoG governments to seek regional solutions. Captain, Cameroon Navy Approved for public release. Distribution is unlimited.

Non-enzymatic browning develops in dry-cooked foods and those with high carbohydrate develop acrylamide, a neurotoxin and potential carcinogen. However, some non-enzymatic browning products have reducing properties. We hypothesized that non-enzymatic browning and reducing power, a measure of antioxidant activity, of processed yam are affected by pre-treatment. Peeled yam cultivars (KM, RKD and SO89) in chunks were pre-soaked (0, 3, 6, 12, 18, and 24 h) in distilled water or pre-blanched (0, 1, 2, 3, 4, and 5 min) in steam. Pre-treated samples were deep-fried at 180 °C for 15 min or roasted at 220 °C for 30 min. Soluble solids, titratable acidity and pH of yam tissues and soaking water were determined. pH of the soaked yam tissues showed a positive relation with non-enzymatic browning. Pre-soaked fried KM and roasted RKD showed a significant decrease in non-enzymatic browning intensities. The reducing power of the cooked yams ranged between 78.94 and 185.92 % of ascorbic acid, and was affected by the different pre-treatment and dry-cooking methods., Highlights • Soaking effectively in decreased non-enzymatic browning in both fried and roasted products of yam varieties. • Blanching affected non-enzymatic browning in the processed yam tissues differently for the different varieties. • pH, titratable acidity and soluble solids are important in non-enzymatic browning of soaked yam tissues. • Pre-treated yams have high reducing power as antioxidant activity. • Reducing power of processed yam is dependent on the variety and the processing method., Yams; blanching; soaking; non-enzymatic browning; reducing power.

In previous studies, we collected roots and soils associated with yam crops (Dioscorea rotundata Poir.) along the Caribbean region of Colombia from which several strains of Azotobacter chroococcum and Azotobacter vinelandii were identified, which in laboratory and nursery studies showed growth promotion activity in yam. In this research, we obtained from Agrosavia two of these strains (A. chroococcum DBC12, A. vinelandii DBC9) and evaluated their effect on yam yields and tuber quality under field conditions, in combination with four nitrogen levels (0, 50, 75 and 100% of the recommended N fertilization dose). In a first instance, in vitro tests confirmed the N fixation capacity and the NH3 production of both bacterial strains, while under field conditions, the highest yields were obtained from treatments that combined the individual inoculation with strains A. chroococcum DBC12 or A. vinelandii DBC9, with 50% of the recommended N fertilization level. On the other hand, yam tubers were classified according to market quality, and the same treatments induced the production of higher yields of first category or export-type tubers, suggesting that these two bacterial strains were also able to improve tuber quality. From this study it was concluded that A. chroococcum DBC12, A. vinelandii DBC9 strains have the potential for replacing up to 50% of the recommended N fertilization dose and present potential as possible bio-inoculants, which could be an alternative for reducing levels of chemical nitrogen fertilization, thus contributing to a more sustainable and competitive yam culture. En estudios previos, realizamos una colecta de raíces y suelos asociados a cultivos de ñame (Dioscorea rotundata Poir) en la región Caribe de Colombia, de los cuales se lograron aislar e identificar varias cepas de Azotobacter chroococcum y Azotobacter vinelandii, que en estudios de laboratorio y casa de malla mostraron promoción del crecimiento en plantas de ñame. Para la presente investigación, se obtuvieron de AGROSAVIA, dos de estas cepas (A. chroococcum DBC12, A. vinelandii DBC9) y se evaluaron, bajo condiciones de campo, sus efectos sobre los rendimientos y la calidad de los tubérculos de ñame, en combinación con la aplicación de cuatro niveles de fertilización química con nitrógeno (0, 50, 75 and 100% de la dosis recomendada para el cultivo). Por un lado, en una primera prueba realizada bajo condiciones in vitro, se confirmó la capacidad de fijación de N y la producción de NH3 en ambas cepas de bacterias, mientras que, bajo condiciones de campo, los más altos rendimientos se obtuvieron con la combinación de la inoculación individual con las cepas A. chroococcum DBC12 o A. vinelandii DBC9, y el 50% de la dosis recomendada de fertilización con nitrógeno. Por otro lado, la clasificación de los tubérculos de ñame de acuerdo con la calidad para el mercado, indicaron que los mismos tratamientos indujeron la producción de una mayor cantidad de tubérculos de primera categoría o calidad tipo exportación, lo que sugiere que estas dos cepas de bacterias son efectivas para mejorar también los aspectos de calidad de los tubérculos. De estos resultados, se concluye que las cepas A. chroococcum DBC12 y A. vinelandii DBC9 tienen la potencialidad de reemplazar hasta el 50% de la dosis recomendada de fertilización nitrogenada y presentan potencial como posibles bioinoculantes, lo que las convierte en una alternativa para reducir los niveles de fertilización química, contribuyendo así a una agricultura más sostenible y competitiva en el cultivo del ñame. Gerencia de Comunicación Institucional, DG SICyP, INTA Fil: Sánchez, D.B. Corporación Colombiana de Investigación Agropecuaria (Agrosavia). Centro de Investigación Turipaná; Colombia Fil: Luna, L.L. Corporación Colombiana de Investigación Agropecuaria (Agrosavia). Centro de Investigación Turipaná; Colombia Fil: Espitia, A.A. Corporación Colombiana de Investigación Agropecuaria (Agrosavia). Centro de Investigación Turipaná; Colombia Fil: Cadena, J. Corporación Colombiana de Investigación Agropecuaria (Agrosavia). Centro de Investigación Turipaná; Colombia

This work aimed to evaluate the influence of the addition of yam flour (Disocorea ssp.) on the color of fresh pasta, as well as its effects on their quality, in addition to proposing a greater added value to the yam, aiming to reduce its loss in Brazilian agribusiness, enabling greater possibilities of use for this tuber and promoting family farming. Four formulations of fresh wholegrain pasta were produced: control pasta (M0), containing 51% whole grain wheat flour (FIT) and 49% refined wheat flour (FRT), and in the other pasta, FB was replaced by flour at levels of 5, 10 and 15% (M1, M2 and M3, respectively). The percentage increase in substitution for yam flour (FI) resulted in lower dough moisture, with M3 being the one that differed statistically from the control dough. Regarding the firmness of raw pasta, the increase in HR increased the hardness of whole pasta, decreased the yield and increased the loss of solids during cooking. M2 was the one that presented quality parameters closest to M0 and was selected to evaluate the antioxidant capacity comparatively with M0. M2 showed higher values of ABTS and DPPH in relation to M0, and they did not differ in the total phenolic content (0.28 µg gallic acid equivalent / mg of dry sample). Yam flour showed a promising potential for use in whole pasta, both technological and functional, which can be beneficial to increase the added value of this tuber. Este trabajo tuvo como objetivo evaluar la influencia de la adición de harina de ñame (Disocorea ssp.) en la coloración de pastas frescas, así como sus efectos en la calidad de las mismas, además de proponer un mayor valor agregado al ñame, a fin de disminuir su perdida en el agronegocio brasileño, permitiendo mayores posibilidades de uso para este tubérculo y promoviendo la agricultura familiar. Fueron producidas cuatro formulaciones de pasta fresca integral: la pasta control (M0), que contuvo 51% de harina de trigo integral (FIT) y 49% de harina de trigo refinada (FRT), y las demás pastas, donde la FRT fue sustituida por la harina de ñame en niveles de 5, 10 y 15% (M1, M2 y M3, respectivamente). El aumento porcentual de la sustitución por la harina de ñame (FI) resultó en masas con menor humedad y rendimiento, siendo M3 la que presentó diferencias estadísticas la masa control. En cuanto a la firmeza de la pasta cruda, el aumento de FI incrementó la dureza de la pasta integral, disminuyó su rendimiento y aumentó la perdida de sólidos durante su cocción. M2 fue la única que presentó parámetros de calidad cercanos a M0, por lo que fue seleccionada para comprar su capacidad antioxidante con el control. M2 presentó mayores valores de ABTS y DPPH en relación con M0, sin embargo, no difirieron en el contenido de fenólicos totales (0.28 µg acido gálico equivalente/mg de muestra seca). La harina de ñame demostró tener potencial, tanto tecnológico como funcional, para ser utilizado en elaboración de pastas integrales, lo que puede ser beneficioso para aumentar el valor agregado de este tubérculo. Este trabalho visou avaliar a influência da adição de farinha de inhame (Disocorea ssp.) sobre a coloração de massas frescas, assim como seus efeitos na qualidade das mesmas, além de propor também um maior valor agregado ao inhame, objetivando diminuir sua perda no agronegócio brasileiro, viabilizando maiores possibilidades de uso para esse tubérculo e promovendo a agricultura familiar. Foram produzidas quatro formulações de massa integral fresca:massa controle (M0), contendo 51% farinha de trigo de grão inteiro (FIT) e 49% de farinha refinada de trigo (FRT), e nas demais massas, a FRT foi substituída pela farinha de inhame nos níveis de 5, 10 e 15% (M1, M2 e M3, respectivamente). O aumento percentual da substituição por farinha de inhame (FI) acarretou em uma menor umidade da massa e rendimento, com aumento da dureza e da perda de sólidos durante o cozimento, sendo a M3 aquela que se diferiu estatisticamente da massa controle. A M2 foi selecionada para avaliar comparativamente a capacidade antioxidante com MO, por os parâmetros de qualidade mais próximos a ela. M2 apresentou maiores valores de ABTS e DPPH em relação à M0, sendo que não diferiram no teor de fenólicos totais (0,28 µg ácido gálico equivalente/mg de amostra seca). A farinha de inhame apresentou potencial promissor para uso em massas integrais, tanto tecnológicos quanto funcionais, o que pode ser benéfico para o aumentar o valor agregado deste tubérculo.

This thesis addresses the history of yam production and markets in Ghana from the 20th century to the present. It explores the changes in the economy of Ghana from the point of view of domestic markets as well as the differences and similitudes between them and the international markets. The history of yams provides new perspectives on the agricultural history of West Africa in relation to the arrival of food crops from other continents and on the history of labour and migrations in relation to the most important cash-crop revolution of the continent: the development of cocoa.; Cette thèse porte sur l'histoire de la production et des marchés de l'igname au Ghana du 20e siècle à nos jours. Elle explore les changements dans l'économie du Ghana du point de vue des marchés domestiques ainsi que les différences et les similitudes entre ces marchés et les marchés internationaux. L'histoire de l'igname offre de nouvelles perspectives sur l'histoire de l'agriculture de l'Afrique de l'Ouest par rapport à l'arrivée de cultures vivrières provenant d'autres continents et sur l'histoire du travail et des migrations par rapport au plus important développement des cultures commerciales du continent : le cacao.

Made available in DSpace on 2022-04-28T19:08:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-04-25 The objective of this study was to evaluate the physiological characteristics of minimally processed yam on the application of edible coating of the starch associated with the addition of ascorbic acid. For this, the minimally processed yam was stored for 12 days at 8±1°C and it underwent five treatments: control - T1; coated only with edible starch - T2; coated only with 1% ascorbic acid - T3; coated with edible starch with 1% ascorbic acid - T4; and coated with 1% ascorbic acid and 1% citric acid - T5. Respiratory rate, evolution of C2H4 and the concentrations of CO2 and ethylene (C2H4) were analyzed. Coated treatments showed the end of the lower storage CO2 concentrations in relation to the treatment in which edible coating was not applied. It was also found that the treatments in which ascorbic acid was incorporated showed higher CO2 release, suggesting its influence as an antioxidant in the respiratory system. Regarding respiratory rate, after finishing the minimal processing were found lower values for treatments with lining, with an average 58% reduction in respiratory rate. After the 4th day, all treatments showed a constant behavior with respect to respiratory rate. Instituto Federal de Sergipe, Rodovia Juscelino Kubitschek, s/n Universidade Federal de Sergipe, Av. Marechal Rondon, s/n Jardim Rosa Elze Universidade Estadual Paulista Campus Jaboticabal, Via de Acesso Prof. Paulo Donato Castellane, s/n Universidade Estadual Paulista Campus Jaboticabal, Via de Acesso Prof. Paulo Donato Castellane, s/n

The genus Paraburkholderia includes a variety of species with promising features for sustainable biotechnological solutions in agriculture through increasing crop productivity. Here, we present a novel Paraburkholderia isolate, a permanent and predominant member of the Dioscoreae bulbifera (yam family, Dioscoreaceae) phyllosphere, making up to 25% of the microbial community on leaf acumens. The 8.5 Mbp genome of isolate Msb3 encodes an unprecedented combination of features mediating a beneficial plant-associated lifestyle, including biological nitrogen fixation (BNF), plant hormone regulation, detoxification of various xenobiotics, degradation of aromatic compounds and multiple protein secretion systems including both T3SS and T6SS. The isolate exhibits significant growth promotion when applied to agriculturally important plants such as tomato, by increasing the total dry biomass by up to 40%. The open question about the “beneficial” nature of this strain led us to investigate ecological and generic boundaries in Burkholderia sensu lato. In a refined phylogeny including 279 Burkholderia sensu lato isolates strain Msb3 clusters within Clade I Paraburkholderia, which also includes few opportunistic strains that can potentially act as pathogens, as revealed by our ecological meta-data analysis. In fact, we demonstrate that all genera originating from the “plant beneficial and environmental” (PBE) Burkholderia species cluster include opportunists. This indicates that further functional examinations are needed before safe application of these strains in sustainable agricultural settings can be assured.

The genus Paraburkholderia includes a variety of species with promising features for sustainable biotechnological solutions in agriculture through increasing crop productivity. Here, we present a novel Paraburkholderia isolate, a permanent and predominant member of the Dioscoreae bulbifera (yam family, Dioscoreaceae) phyllosphere, making up to 25% of the microbial community on leaf acumens. The 8.5 Mbp genome of isolate Msb3 encodes an unprecedented combination of features mediating a beneficial plant-associated lifestyle, including biological nitrogen fixation (BNF), plant hormone regulation, detoxification of various xenobiotics, degradation of aromatic compounds and multiple protein secretion systems including both T3SS and T6SS. The isolate exhibits significant growth promotion when applied to agriculturally important plants such as tomato, by increasing the total dry biomass by up to 40%. The open question about the "beneficial" nature of this strain led us to investigate ecological and generic boundaries in Burkholderia sensu lato. In a refined phylogeny including 279 Burkholderia sensu lato isolates strain Msb3 clusters within Clade I Paraburkholderia, which also includes few opportunistic strains that can potentially act as pathogens, as revealed by our ecological meta-data analysis. In fact, we demonstrate that all genera originating from the "plant beneficial and environmental" (PBE) Burkholderia species cluster include opportunists. This indicates that further functional examinations are needed before safe application of these strains in sustainable agricultural settings can be assured.

As dioscoreáceas constituem uma importante fonte alimentar e estão distribuídas nas regiões tropicais e subtropicais de todo o mundo. O objetivo desta pesquisa foi realizar um estudo etnobotânico sobre as variedades de cará (Dioscorea spp.) cultivadas por agricultores de oito municípios da Baixada Cuiabana, em Mato Grosso, com o intuito de verificar as espécies mantidas por eles e suas diversidades, nomes populares das variedades e o sistema de produção da cultura como: preparo das túberas-sementes, manejo da cultura, preparo do solo, plantio, tratos culturais e comercialização. Foram entrevistados 48 agricultores que cultivam o cará e anotados os nomes populares que estes dão às variedades do tubérculo. Foram encontradas três espécies: Dioscorea alata, D. trifida e D. bulbifera. O cultivo do cará é feito no sistema de ?roça de toco?. O preparo das túberas-sementes varia de acordo com cada espécie, sendo que, das 3 espécies encontradas, 55% são plantadas partidas e 45% inteiras. A organização e destino da produção acontecem nas comunidades, onde grande parte é destinada à alimentação familiar e o excedente é para a venda direta para consumidores ou via intermediários e aqueles que produzem exclusivamente para a venda. The yam is an important food source and are distributed worldwide in tropical, subtropical and temperate regions. The objective of this research was to conduct an ethnobotanical study on yam (Dioscorea spp.) varieties grown by farmers from eight municipalities of the Baixada Cuiabana, in Mato Grosso State, in order to verify the species kept by them and their diversity, popular names of the varieties and the crop?s production system, such as: seed tubers management, crop management, soil tillage, planting, cultivation and marketing. We interviewed 48 farmers, taking note of the popular names given to the yam varieties. Three species were found in the studied area: Dioscorea alata, D. trifida and D. bulbifera. The cultivation of yams is done on a "slash and burn" agriculture system. The preparation of the seed tubers varies with each species, whereas 55% are planted after being cut and 45% as whole tubers. The organization of production and destination occur in the communities, where most of it is destined for the families own consumption and the surplus is for sale directly to consumers or via intermediaries. Made available in DSpace on 2020-05-09T04:39:59Z (GMT). No. of bitstreams: 1 26994.pdf: 267993 bytes, checksum: 4e2c16ce333b28f31e5b50daec4075a2 (MD5) Previous issue date: 2020

Whole genome duplication (WGD) events are common in many plant lineages, but the ploidy status and possible occurrence of intraspecific ploidy variation are unknown for most species. Standard methods for ploidy determination are chromosome counting and flow cytometry approaches. While flow cytometry approaches typically use fresh tissue, an increasing number of studies have shown that recently dried specimens can be used to yield ploidy data. Recent studies have started to explore whether high-throughput sequencing (HTS) data can be used to assess ploidy levels by analyzing allelic frequencies from single copy nuclear genes. Here, we compare different approaches using a range of yam (Dioscorea) tissues of varying ages, drying methods and quality, including herbarium tissue. Our aims were to: (1) explore the limits of flow cytometry in estimating ploidy level from dried samples, including herbarium vouchers collected between 1831 and 2011, and (2) optimize a HTS-based method to estimate ploidy by considering allelic frequencies from nuclear genes obtained using a target-capture method. We show that, although flow cytometry can be used to estimate ploidy levels from herbarium specimens collected up to fifteen years ago, success rate is low (5.9%). We validated our HTS-based estimates of ploidy using 260 genes by benchmarking with dried samples of species of known ploidy (Dioscorea alata, D. communis, and D. sylvatica). Subsequently, we successfully applied the method to the 85 herbarium samples analyzed with flow cytometry, and successfully provided results for 91.7% of them, comprising species across the phylogenetic tree of Dioscorea. We also explored the limits of using this HTS-based approach for identifying high ploidy levels in herbarium material and the effects of heterozygosity and sequence coverage. Overall, we demonstrated that ploidy diversity within and between species may be ascertained from historical collections, allowing the determination of polyploidization events from samples collected up to two centuries ago. This approach has the potential to provide insights into the drivers and dynamics of ploidy level changes during plant evolution and crop domestication.

Dry root disease of yam (Dioscorea spp.), caused by Scutellonema bradys, Pratylenchus coffeae and brachyurus, isprominent among the plant disease problems of yam in Brazil. In order to evaluate the association of these nematode species withweeds, field sampling was performed during 2016 and 2017 in yam-growing areas with a history of the disease within the majorcounties in the state of Alagoas, Brazil. The frequency of occurrence of both weeds and nematodes was determined, in addition tothe estimated population of nematodes in roots. Forty-three weed species were found, of which 23 were infected with at least one ofthe causal agents of the dry rot disease, Pratylenchus spp. being the most prevalent in the fields. Ageratum conyzoides, Commelina benghalensisandEmilia coccinea (in Zona da Mata) and C. benghalensis (Agreste region) were especially important due to theirhigh frequency of occurrence and also for supporting populations of bradysan Pratylenchus spp. Cyperus flavus, coccinea and permacoce verticillataare now recorded as new weed species associated with. bradys. Made available in DSpace on 2020-01-15T00:37:19Z (GMT). No. of bitstreams: 1 Marissonia.NEMY3255DeAlmeida.pdf: 190800 bytes, checksum: 7558f1ac8512666fd7f56dcc2516f709 (MD5) Previous issue date: 2019

Home gardens are considered as vital units for enhancing food security particularly in developing nations of South Asia, such as Sri Lanka. Although the yam crop Dioscorea spp. constitute a popular but still minor component in Sri Lankan home gardens, they have the potential of producing large quantities of edible material with minimal inputs. However, their real value in South Asian home gardens is not yet reported. Hence, this study was carried out to get insights into home garden characteristics, gardener demography as well as current management practices within 300 Sri Lankan home garden systems that are located along a climatic gradient. By using interviews and field observations, gardeners, who cultivated in particular Dioscorea species, were studied within 10 of the 25 administrative districts distributed in the wet, intermediate and dry climatic zone of Sri Lanka. Furthermore, current management practices of yams cultivation were analyzed on local scale and compared afterwards with management recommendations published in the year 2006 by the Department of Agriculture. Dioscorea species were found in a majority of home gardens, especially in wet and intermediate zones of Sri Lanka. D. alata was the most prominent species and was managed at a subsistence level and not as per recommendations developed by the Department of Agriculture. Our results revealed that Dioscorea alata is an essential component of Sri Lankan home gardens in rural areas and can yield substantial quantities of edible tubers with low input, especially during times of food scarcities, and has therefore the potential to enhance food security and rural development.

Background Dioscorea is a widely distributed and highly diversified genus in tropical regions where it is represented by ten main clades, one of which diversified exclusively in Africa. In southern Africa it is characterised by a distinct group of species with a pachycaul or “elephant’s foot” structure that is partially to fully exposed above the substrate. In contrast to African representatives of the genus from other clades, occurring mainly in forest or woodland, the pachycaul taxa and their southern African relatives occur in diverse habitats ranging from woodland to open vegetation. Here we investigate patterns of diversification in the African clade, time of transition from forest to more open habitat, and morphological traits associated with each habitat and evaluate if such transitions have led to modification of reproductive organs and mode of dispersal. Results The Africa clade originated in the Oligocene and comprises four subclades. The Dioscorea buchananii subclade (southeastern tropical Africa and South Africa) is sister to the East African subclade, which is respectively sister to the recently evolved sister South African (e. g., Cape and Pachycaul) subclades. The Cape and Pachycaul subclades diversified in the east of the Cape Peninsula in the mid Miocene, in an area with complex geomorphology and climate, where the fynbos, thicket, succulent karoo and forest biomes meet. Conclusions Diversification out of forest is associated with major shifts in morphology of the perennial tuber (specifically an increase in size and orientation which presumably led them to become pachycaul) and rotation of stem (from twining to non-twining). The iconic elephant's foot morphology, observed in grasslands and thicket biomes, where its corky bark may offer protection against fire and herbivory, evolved since mid Miocene. A shift in pollination trait is observed within the forest, but entry into open habitat does not show association with reproductive morphology, except in the seed wing, which has switched from winged all round the seed margin to just at the base or at the apex of it, or has been even replaced by an elaiosome. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0812-z) contains supplementary material, which is available to authorized users.

13 páginas, 4 figuras, 5 tablas., Aim The Chilean endemic Dioscorea biloba (Dioscoreaceae) is a dioecious geophyte that shows a remarkable 600 km northsouth disjunction in the peripheral arid area of the Atacama Desert. Its restricted present-day distribution and probable Neogene origin indicate that its populations have a history linked to that of the Atacama Desert, making this an ideal model species with which to investigate the biogeography of the region. Location Chile, Atacama Desert and peripheral arid area. Methods Two hundred and seventy-five individuals from nine populations were genotyped for seven nuclear microsatellite loci, and plastid trnLF and trnTL sequences were obtained for a representative subset of these. Analyses included the estimation of genetic diversity and population structure through clustering, Bayesian and analysis of molecular variance analyses, and statistical parsimony networks of chloroplast haplotypes. Isolation by distance was tested against alternative dispersal hypotheses. Results Microsatellite markers revealed moderate to high levels of genetic diversity within populations, with those from the southern Limari Valley showing the highest values and northern populations showing less exclusive alleles. Bayesian analysis of microsatellite data identified three genetic groups that corresponded to geographical ranges. Chloroplast phylogeography revealed no haplotypes shared between northern and southern ranges, and little haplotype sharing between the two neighbouring southern valleys. Dispersal models suggested the presence of extinct hypothetical populations between the southern and northern ranges. Main conclusions Our results are consistent with prolonged isolation of the northern and southern groups, mediated by the life-history traits of the species. Significant isolation was revealed at both large and moderate distances as gene flow was not evident even between neighbouring valleys. Bayesian analyses of microsatellite and chloroplast haplotype diversity identified the southern area of Limari as the probable area of origin of the species. Our data do not support recent dispersal of D. biloba from the southern range into Antofagasta, but indicate the fragmentation of an earlier wider range, concomitant with the Pliocene-Pleistocene climatic oscillations, with subsequent extinctions of the Atacama Desert populations and the divergence of the peripheral ones as a consequence of genetic drift., We thank E. Pérez-Collazos and L. Villar for their help during fieldwork. A. Díaz-Pérez for his valuable comments and discussion on dispersal model analysis, P. Gibbs and T. Langdon for their linguistic assistance, and the editor P. Ladiges and two anonymous referees for their valuable comments that have improved the manuscript. This study has been supported by a Fundación BBVA BIOCON 05-093/06 project grant. J.V. was supported by a Fundación BBVA PhD grant, an Instituto de Estudios Altoaragoneses project, and two research stays at Royal Botanic Gardens, Kew, funded by SYNTHESYS GB-TAF and the Diputación General de Aragón-Caja de Ahorros de la Inmaculada (DGA-CAI). J.G.S.-M. was supported by two consecutive Spanish Aragón Government ‘Araid’ and Ministry of Science and Innovation ‘Ramón y Cajal’ post-doctoral contracts.

Cet article, qui présente le travail horticole et une partie des responsabilités rituelles des hommes à Wallis (Polynésie occidentale), porte sur les ignames (mise en culture, classifications indigènes, système rituel et circuits d’échange) et montre que ces tubercules participent d’un vaste système de relations qui définissent tout être en référence à la société wallisienne dont le « roi » scelle l’ensemble de l’organisation. Comparables à des enfants masculins que les hommes obtiennent de leurs jardins, les ignames concourent, en circulant dans les échanges, à la constitution différenciée des vivants, au renouvellement du monde et à la pérennisation de la société. This paper describes a part of the men’s responsibilities, both agricultural and ritual, in Wallis Island, Western Polynesia. Yams are the main focus of this study including agricultural techniques, indigenous classifications, ritual system and exchange pathways. It shows that yams are involved in a large system of relationships that defines everything in relation with the society itself. Comparable to sons that men would get from their gardens, these tuber partake, by circulating in exchanges, in the differentiated constitution of living people, the world’s renewing and the society’s everlastingness.

Loss of varietal diversity is a worldwide challenge to crop species at risk for genetic erosion, while the loss of biological resources may hinder future breeding objectives. Loss of varieties has been mostly investigated in traditional agricultural systems where variety numbers are dramatically high, or for most economically important crop species for which comparison between pre-intensive and modern agriculture was possible. Varietal dynamics, i.e., turnover, or gains and losses of varieties by farmers, is nevertheless more rarely studied and while we currently have good estimates of genetic or varietal diversity for most crop species, we have less information as to how on farm agro-diversity changes and what cause its dynamics. We therefore investigated varietal dynamics in the agricultural yam system in the Caribbean island of Guadeloupe. We interviewed producers about varieties they cultivated in the past compared to their current varieties, in addition to characterizing yam cropping characteristics and both farm level and producers socio-economic features. We then used regression tree analyses to investigate the components of yam agro-diversity, varietal dynamics and impact of anthracnose on varieties. Our data demonstrated that no dramatic loss of varieties occurred within the last decades. Cultivation changes mostly affected widespread cultivars while frequency of uncommon varieties stayed relatively stable. Varietal dynamics nevertheless followed sub-regional patterns, and socio-economic influences such as producer age or farm crop diversity. Recurrent anthracnose epidemics since the 1970s did not alter varietal dynamics strongly, but sometimes translated into transition from Dioscorea alata to less susceptible species or into a decrease of yam cultivation. Factors affecting changes in agro-diversity were not relating to agronomy in our study, and surprisingly there were different processes delineating short term from long term varietal dynamics, independently of disease risk. Our results highlighted the importance of understanding varietal dynamics, an often overlooked component of agriculture sustainability, in addition to evolutionary forces shaping agro-diversity and genetic diversity distribution within crops. It is also crucial to understand how processes involved do scale up worldwide and for different crop species, so as not to mislead on-farm conservation efforts and efficacy of agro-diversity preservation.

Aim: Dioscorea (Dioscoreaceae) is a predominantly pantropical genus (, This study was supported by Fundación BBVA (FBBVA) BIOCON 05-093/ 06 project (PC, JGSM) and by Instituto de Estudios Altoaragoneses project (J.V.). J.V. benefited from a PhD fellowship funded by FBBVA and two research stays at Kew Gardens funded by European SYNTHESYS GB-TAF and DGA-CAI grants. J.G.S-M. was supported by Araid and Ramón y Cajal postdoctoral contracts. P.C. was partially funded by Bioflora Research Team grant cofunded by the Aragón Government and the European Social Fund. I.S. was supported by grant CGL2012-40129-C02-01 from the Spanish Ministry of Science.

Background Dioscorea is a widely distributed and highly diversified genus in tropical regions where it is represented by ten main clades, one of which diversified exclusively in Africa. In southern Africa it is characterised by a distinct group of species with a pachycaul or “elephant’s foot” structure that is partially to fully exposed above the substrate. In contrast to African representatives of the genus from other clades, occurring mainly in forest or woodland, the pachycaul taxa and their southern African relatives occur in diverse habitats ranging from woodland to open vegetation. Here we investigate patterns of diversification in the African clade, time of transition from forest to more open habitat, and morphological traits associated with each habitat and evaluate if such transitions have led to modification of reproductive organs and mode of dispersal. Results The Africa clade originated in the Oligocene and comprises four subclades. The Dioscorea buchananii subclade (southeastern tropical Africa and South Africa) is sister to the East African subclade, which is respectively sister to the recently evolved sister South African (e. g., Cape and Pachycaul) subclades. The Cape and Pachycaul subclades diversified in the east of the Cape Peninsula in the mid Miocene, in an area with complex geomorphology and climate, where the fynbos, thicket, succulent karoo and forest biomes meet. Conclusions Diversification out of forest is associated with major shifts in morphology of the perennial tuber (specifically an increase in size and orientation which presumably led them to become pachycaul) and rotation of stem (from twining to non-twining). The iconic elephant's foot morphology, observed in grasslands and thicket biomes, where its corky bark may offer protection against fire and herbivory, evolved since mid Miocene. A shift in pollination trait is observed within the forest, but entry into open habitat does not show association with reproductive morphology, except in the seed wing, which has switched from winged all round the seed margin to just at the base or at the apex of it, or has been even replaced by an elaiosome.

This paper revisits the extent of seasonality in African livelihoods. It uses 19 years of monthly food prices from 20 markets and three years of nationally representative household panel surveys from Tanzania. Trigonometric specifications are introduced to measure the seasonal gap. When samples are short and seasonality is poorly defined, they produce less upward bias than the common dummy variable approach. On average, the seasonal gap for maize prices is estimated to be 27 percent; it is 15 percent for rice. In both cases it is two and a half to three times higher than in the international reference market. Food price seasonality is not a major contributor to food price volatility, but it does translate into seasonal variation in caloric intake of about 10 percent among poor urban households and rural net food sellers. Rural net food-buying households appear able to smooth their consumption. The disappearance of seasonality from Africas development debate seems premature.

Agriculture is the dominant sector of the economy, contributing a third of the country’s gross domestic product (GDP) and about half of Rwanda’s export earnings. The government of Rwanda has therefore made agricultural development a priority and allocated significant resources to improving productivity, expanding the livestock sector, promoting sustainable land management, and developing supply chains and value-added activities. At the same time, Rwanda’s agriculture sector faces a series of challenges. Agriculture is dominated by small-scale, subsistence farming under traditional agricultural practices and rain-fed agriculture. As a result, average crop yields are low compared with potential yields, and exposed to risks such as weather related shocks and pest and disease outbreaks. The purpose of this report is to assess existing risks to the agriculture sector, prioritize them according to their frequency and impacts on the sector, and identify areas of risk management solutions that need deeper specialized attention. Three levels of risks are assessed: production risks, market risks, and enabling environment risks to selected supply chains. The report takes a quantitative and qualitative approach to risks. The report is structured as follows: chapter one gives introduction. Chapter two provides an overview of Rwanda’s economy and the role and structure of the agriculture sector. Agriculture sector risks (production, market, and enabling environment risks) for the selected food crops, export crops, and livestock are analyzed in chapter three. Analysis of the adverse impacts of agricultural risks at aggregate and provincial levels, along with a stakeholder risk assessment and a discussion of particularly vulnerable groups, is presented in chapter four. Chapter five prioritizes identified risks, discusses potential solutions areas, summarizes feedback from consulted stakeholders, and recommends solutions areas for further assessment.

Despite recent calls in support of cash transfers, there is little rigorous evidence of the relative impacts of cash versus in-kind transfers, especially in humanitarian contexts, where a majority of such programs take place. This paper uses data from a randomized experiment in the Democratic Republic of Congo to assess the relative impacts and costs of equivalently valued cash and voucher transfers. The voucher program distorted households’ purchases along both the extensive and intensive margin as compared with unconstrained cash households. Yet there were no differences in food consumption or other measures of well-being, in part due to the fact that voucher households were able to resell part of what they purchased. As there were no significant benefits to vouchers, cash transfers were the more cost effective modality for both the implementing agency and program recipients in this context.

Agricultural risk management is a central issue that Mozambique faces in development, and multiple stakeholders have analyzed this challenge, sometimes with different terminology and focusing on varying aspects. The government of Mozambique has adopted the strategic plan for agricultural development (PEDSA 2010-19) that focuses on: (i) increasing the availability of food in order to reduce hunger through growth in small producer productivity and emergency response capacity; (ii) enlarging the land area under sustainable management and the number of reliable water management systems; (iii) increasing access to the market through improved infrastructures and interventions in marketing; and (iv) improving research and extension for increased adoption of appropriate technologies by producers and agro-processors. The World Bank’s agriculture sector risk assessment takes a holistic approach and relies on long time-series historical data to arrive at an empirical and objective assessment of agricultural risks and their impacts on Mozambique. This assessment will form the basis of the second step, solution assessment, whose final findings will inform National Investment Plan for the Agrarian Sector in Mozambique (PNISA). This document considers the many aspects of assessing risk in the Mozambican agriculture sector. Chapter one gives introduction and context. Chapter two introduces the major characteristics of the agricultural system leading into chapter three, which presents a comprehensive picture of the risks that exist in the sector. Chapter four, in quantifying the risks that have been observed, comments on the losses that have been incurred by the sector because of production risks, whereas chapter five provides a qualitative discussion of how risk has an effect on the different stakeholders present in the sector. Chapter six delves into the risk prioritization carried out by the team and then comments on various management measures. The report concludes with chapter six, in which recommendations are provided for improving risk management in Mozambique.

The report Africa Can Help Feed Africa (World Bank 2012) showed that increasing food staples1 supply can be met by better connecting African markets to each other. That report called for a stronger focus on removing trade barriers and building on the forces of regional integration. This report builds on the lessons of Africa Can Help Feed Africa by looking into the specific circum¬stances met in West Africa, home to one-third of the continent’s population and to some of its most vulnerable countries. Staple foods are the main source of calories in Africa and in West Africa. In that region, rice, followed by maize and cassava, provides the main source of calories in coastal countries, with millet and sorghum being an important source of food in Sahelian countries (Haggblade et al. 2012). The challenge of food supply is particularly acute in West Africa with some of the world’s fastest growing populations, including urban populations. West Africa’s 2011 population of 342 million is expected to increase to 516 million by 2030 and to 815 million by 2050 (United Nations Department of Economic and Social Affairs, Population Division 2013); in this time frame, the region’s urban population will grow from 44 percent to 63 percent of the total population (United Nations Department of Economic and Social Affairs, Population Division 2014). As this report will show, strong reasons exist to bring a more strategic focus on promoting regional trade. The first compelling reason is that there is already a sizeable amount of trade in the region, revealing existing important complementarities between countries in the ECOWAS space. Because a large share of this trade is informal, this reality is not always well taken into account. A second reason is that developing these complementarities by facilitating trade and creating the regional soft and hard infra¬structure to incite cross-border flows would further enable (a) the exploitation of comparative advan¬tages and economies of scale in the region; (b) access to and diffusion of better production technologies; (c) competitive access to inputs, research, and extension services; and (d) improved security in the face of shocks that lead to food crises. Finally, a third reason is that existing national policies that affect trade are, by and large, inefficient and incoherent at the regional level; therefore a better use of policy making and institutions is needed to achieve food policy objectives.

This report is the result of a World Bank mission that visited Paraguay in June 2013 at the request of the Government of Paraguay. The mission’s objective was to identify, quantify, and prioritize agriculture risks that determine the volatility of agriculture gross domestic product (GDP), based on a methodology to assess sector risks developed by the World Bank. The methodology stipulates a two-phase process. The first phase (risk evaluation), which is in volume one of this report, was reviewed by the government and evaluates the current situation and perspective of agriculture sector risks, starting from the standpoint of supply chains. From here, and based on the identification of the most important risks, given their frequency and severity, a list of possible solutions was produced in addition to the existing public and private programs and policies. This process is completed with a second phase, where an action plan was prepared (volume two) that can be executed in the medium term to reduce sector risks and to contribute to the sustainability of agriculture investments. The significant efforts undertaken by the government to maintain support programs in critical production and trade areas of the sector are recognized, as well as the institutional development to strengthen the response capacity to agriculture risks. Chapter one gives introduction. Chapter two presents information about the agriculture sector and its recent performance is included, allowing to determine the most important supply chains for this risk assessment and to place the relative economic and social importance of the various commodities and production methods in the appropriate context. In chapter three, a comprehensive assessment of production, market, and enabling environment risks is undertaken for the main commercial and family farming supply chains, in addition to livestock. Chapter four shows the repercussions that risks have had in the past, in particular aggregated losses incurred by supply chain actors. Chapter five assesses the impacts of these losses throughout the supply chains and explores the relative vulnerability of the different actors. Chapter six presents the results and ranking of risks, a list of possible solutions jointly with different public initiatives where some identified risks are addressed.

The study analyzed the price behavior of major staple foods in West Africa taking Nigeria as a case study (1966 – 2011). It described the trend of the major staple food prices and examined the linear relationship and interdependence of the major staple food prices in Nigeria. Secondary data were used for this study. The sources were; Food and Agriculture Organization (FAO), and National Bureau of Statistics (NBS). These data were transformed from their nominal value to real value and analyzed using descriptive statistics, unit root test, Pearson correlation coefficient, granger-causality test and structural equation model. The study revealed that the prices of most of the major staple foods were at the maximum value between 1991 and 1993 while their prices were at the minimum value between 1978 and 1983. The study observed that the price of cowpea is most volatile seconded by maize. The results of the unit root test showed that all the variables studied were stationary. The prices of the major staple foods were linearly correlated; some were positively correlated while some were negatively correlated. Granger-causality test on the major staple foods prices showed that the prices of most staple foods were unidirectional while only few were bi-directional. The study further revealed that the prices of staple foods were interdependent. The study recommends political stability in the country as the major staple food prices reached maximum level during the period of 1993 presidential election crisis.

Comme l’indique Barrau, une synergie terre-mère s’effectue en Mélanésie par une relation d’équivalence entre deux récoltes, celles de poissons et celles de légumes. Les Lau de Malaita fondent cette convertibilité au moyen du mythe d’origine de l’igname. Dérobé aux esprits, le tubercule se transforme en poisson. Or ses écailles ressemblent aux coupures en lesquelles on détaille l’igname pour la planter. Jetées sur un tas d’ordures, les écailles germent et implantent ainsi l’igname à Malaita. On développe donc une métaphore en métamorphose qui génère un mythe d’origine, qu’on peut interpréter comme la charte des marchés traditionnels. Là, opératrices de la synergie terre-mer, les femmes transforment les produits marins en produits de la terre et inversement. Barrau has concisely made the point that both sea and land are harvested equivalently and yield interchangeable crops. The Lau of Malaita had long shared the same view and have expressed it in their myth of origin of the yam. Culture heroes steal tubers from the island of spirits that, angry, sink their get-away boat. Fallen in the sea, the yam turns into a big fish. Back home, the heroes catch the fish, throw its scales on a garbage heap. The scales, similar to the cuttings into which yam tubers are sliced for planting, germinate and thus bring yam to Malaita. The Lau have developed that metaphor (scales = cuttings) into a metamorphosis that generates a myth of origin. The myth can be interpreted as the charter of the institutionalized markets where, in everyday life, women implement the metamorphosis of fish into vegetables and vice-versa, and thus act as the operators of the land-sea synergy.

Cet article aborde les transformations de la cérémonie collective des prémices dans la moyenne vallée du pays Mèa en Nouvelle-Calédonie avant la mise en place des « réserves ». Sur une durée qui n’a pas dû excéder une soixantaine d’années, trois formes cérémonielles se seraient succédées. Elles ont dû correspondre à l’intégration d’événements qui ont parfois été le pendant de transformations de l’organisation sociale. Il aurait alors été recouru au dédoublement de structures binaires par des structures ternaires. « First fruit ceremonies, social integration and binary versus ternary models in Mea country (New Caledonia) » deals with three different types of first fruit ceremony which were successively staged in the middle part of the Mea valley, up until colonization put and end to an autonomous activity of its own. These ceremonies which succeeded one another over a period which can not have exceeded sixty years, must have been resorted to as means of integrating recently occured events : ternary models would then have been put forward as a substitute to binary sets of organization.

Nous avons fait le pari de remonter le temps d’une histoire du manger et du boire dans les monts Mandara. Île montagnarde plantée dans le bassin tchadien, elle a enregistré les diffusions de plantes en décalage par rapport aux plaines environnantes, mais par conservatisme ses populations en ont entretenu plus longtemps la culture. Ce milieu contraint a suscité à partir de parcs arborés précisément sélectionnés des formes d’extractivisme très contrôlées.Ces humanités montagnardes ont évolué et avec elles leurs agrosystèmes. Nous avons retenu dans ces sociétés autarciques, trois grandes « époques agraires » et partant alimentaires. La première prend l’aspect d’une horticulture de montagne avec des ignames et de petits tubercules ; elle sera peu à peu gagnée par une céréaliculture d’éleusines et de mils pénicillaires pour aboutir au complexe agricole céréalier de sorghos de ces derniers siècles. Depuis « les commencements » un ensemble oléo-protéinagineux centré sur les niébés a favorisé ces différents modes d’agricultures montagnardes. Ces légumineuses ont soutenu la diète des populations quelles que soient les associations et les rotations culturales découlant de disciplines portées par des choix aussi sociaux qu’économiques.Jouant sur des faisceaux d’indices nous n’avons pu envisager que de probables successions de combinaisons agraires qui attendent dès lors d’être infirmées ou confirmées par des démarches disciplinaires autorisées à marquer le temps. Our intention in the present paper is to go back in time and lay out the history of eating and drinking in the Mandara Mountains. Located in the Chad Basin area, the Mandara Mountains often lag behind the neighbouring plains when it comes to the diffusion of plants, even though they did manage to maintain these crops over longer periods of time. Such an enclosed environment only allowed a selected vegetation to grow, from which specific and controled collecting methods have developed.These mountain dwellers have evolved together with their agrosystems over time. This history can be divided into three major periods. The first one is characterized by a mountain horticulture with yams, small tubers, gradually replaced by cereals such as eleusines and millets (Pennisetum glaucum), and finally ending in the Sorghum complex of the last past centuries. Since the remotest times, a set of crops focused on cowpeas (Vigna unguiculata) have allowed these diverse ways of moutain farming to develop. Such leguminous plants formed the basis of the local diet, irrespective of the associations and rotations of crops stemming from social or economic considerations.We have only been able here to point out probable successions of agricultural combinations which are now awaiting further investigations from other disciplines such as archaeology in order to be confirmed or not.

Dioscorea trifida L. (Dioscoreaceae) is among the economically most important cultivated Amerindian yam species, whose origin and domestication are still unresolved issues. In order to estimate the genetic diversity maintained by traditional farmers in Brazil, 53 accessions of D. trifida from 11 municipalities in the states of São Paulo, Santa Catarina, Mato Grosso and Amazonas were characterized on the basis of eight Simple Sequence Repeats (SSR) and 16 Inter Simple Sequence Repeats (ISSR) markers. The level of polymorphism among the accessions was high, 95% for SSR and 75.8% for ISSR. The SSR marker showed higher discrimination power among accessions compared to ISSR, with D parameter values of 0.79 and 0.44, respectively. Although SSR and ISSR markers led to dendrograms with different topologies, both separated the accessions into three main groups: I—Ubatuba-SP; II—Iguape-SP and Santa Catarina; and III—Mato Grosso. The accessions from Amazonas State were classified in group II with SSR and in a separate group with ISSR. Bayesian and principal coordinate analyzes conducted with both molecular markers corroborated the classification into three main groups. Higher variation was found within groups in the AMOVA analysis for both markers (66.5 and 60.6% for ISSR and SSR, respectively), and higher Shannon diversity index was found for group II with SSR. Significant but low correlations were found between genetic and geographic distances (r=0.08; p=0.0007 for SSR and r=0.16; p=0.0002 for ISSR). Therefore, results from both markers showed a slight spatially structured genetic diversity in D. trifida accessions maintained by small traditional farmers in Brazil.

Cette contribution montre la diversité et l’évolution des cultures consacrées à la fois à la consommation interne et à l’exportation chez les Dii de l’Adamaoua. L’accent est mis sur les ignames qui ont fait connaître les Dii chez leurs voisins. L’exportation de cultures vivrières est attestée depuis la première mention des Dii dans la littérature, à la fin du XIXe siècle, et s’est perpétuée jusqu’à aujourd’hui. Cependant, la situation est beaucoup plus compliquée que ne le laissent entendre quelques clichés très répandus sur les Dii, mais réducteurs. This article will attempt to show the diversity and evolution of crops cultivated for both internai use and exportation among the Dii of Adamaoua. Emphasis will be put on yams which have attracted the attention of the neighbours of the Dii. Exportation of crops is attested since the first mention of the Dii in the literature, at the end of the nineteenth century, and it is still practised. However, the present situation is far more complicated than some simplistic opinions on the Dii would suggest.

Wild yam species tubers of Ivory Coast are categorized by principal component analyses (PCAs) of nutrients and antinutritional factors and yams cluster analyses (CAs), which agree. Species group into three classes. Compositional PCA and yams CA allow classifying them and agree. The first PCA axis explains 90% of variance. Meta-analysis allows increasing samples numbers and data variety. Different yam behaviour depends on energy. Most antinutritional factors are grouped into the same class. Especies de tubérculos de batatas silvestres de Costa de Marfil se clasifican por análisis de componentes principales (ACPs) de nutrientes y factores antinutricionales y análisis de agregados (AAs) de batatas, los cuales están de acuerdo. Las especies se agrupan en tres clases. El ACP composicional y AA de batatas permiten clasificarlos y están de acuerdo. El primer eje de ACP explica el 90% de la varianza. El metaanálisis permite aumentar el número de muestras y variedad de datos. El comportamiento de diferentes batatas depende de la energía. La mayoría de los factores antinutricionales se agrupan en la misma clase. Ciencias Experimentales

The rural sector, defined here as the economic sector that falls under the scope of the Ministry of Agriculture and Water (MAH), the Ministry of Animal Resources (MRA), and the Ministry of the Environment and Sustainable Development (MEDD), is one of the pillars of the Burkina Faso economy. Although its contribution to GDP has decreased in recent times from 35 percent in 1999 to 30 percent in 2011 due to the development of the other sectors of the economy, agricultural activity still employs approximately 86 percent of Burkina Faso s labor force and is the main source of income for poorer populations. Consequently, the rural sector is among the primary beneficiaries of public expenditures by the Burkina Faso government and constitutes one of the pillars of the Strategy for Accelerated Growth and Sustainable Development (SCADD) adopted in 2010. The goals of this agriculture public expenditure review in Burkina Faso are as follows: draw lessons from the past in terms of budget execution in the agricultural sector in order to promote the design and implementation of public expenditure programs that are more efficient and more equitable and have a greater impact; initiate the implementation of the databases and methodology required to conduct similar reviews regularly and thus contribute to the institutionalization of the process; and contribute to establishing the conditions for increased support for the sector while encouraging the harmonization and alignment of support with respect for national strategies.

Several viral species infecting cultivated yams (Dioscorea spp.) are known. They include viruses belonging to the families Alphaflexiviridae (genus Potexvirus), Betaflexiviridae (genus Carlavirus), Caulimoviridae (genus Badnavirus), Cucumoviridae (genus Cucumovirus) and Potyviridae (genera Macluravirus and Potyvirus). However, it is widely acknowledged that yet uncharacterized viral species are present in yam germplasm collections worldwide and could be propagated through the distribution of infected germplasm. Therefore, viruses are currently the major constraint for much needed exchanges and distribution of yam germplasm. In order to promote the safe exchange of yam germplasm conserved in the Guadeloupe Biological Resources Center of Tropical Plants (CRB-PT), searches for new virus species in yams were undertaken. In silico analyses of ESTs of Dioscorea alata were performed and unveiled the existence of sequences corresponding to several known genera of yam viruses, such as Badnavirus and Macluravirus, and also to families of unknown yam-associated viruses, including Geminiviridae and Secoviridae. RT-PCR were performed on crude extracts of symptomatic yams (D. alata, D. trifida) following direct binding of viral particles and using degenerate primers. Amplification products were cloned and sequenced. Some of them displayed significant levels of homology with potexviruses and with viruses of the family Secoviridae. The 3' ends of the corresponding viral genomes were successfully amplified by 3' RACE, cloned and sequenced. Phylogenetic analyses confirmed the existence in yams of one new viral species within the genus Potexvirus (tentatively named Yam virus X, YVX) and one within the family Secoviridae (tentatively named Yam necrosis virus, YNV). The experimental host range of both viruses was explored through mechanical inoculation on various herbaceous plants. Molecular diagnostic was developed for both YVX and YNV using direct binding reverse transcription PCR (DB-RT-PCR) and used to perform a prevalence study of both viruses in the Guadeloupe CRB-PT yam germplasm collection. (Texte intégral)

The Pacific Region is one of the most natural disaster prone regions on earth. The Pacific Island Countries (PICs) are highly exposed to the adverse effects of climate change and natural hazards, which can result in disasters affecting their entire economic, human, and physical environment and impact their long-term development agenda. The average annual direct losses caused by natural disasters are estimated at US$284 million. Since 1950 natural disasters have affected approximately 9.2 million people in the Pacific Region, causing 9,811 reported deaths. This has cost the PICs around US$3.2 billion (in nominal terms) in associated damage costs. This report focuses on the development of the country catastrophe risk profiles, the information collected, how it was catalogued and processed, and now being used for a variety of applications in Climate and Disaster Risk Management. The country risk profiles integrate data collected and produced through risk modeling and include maps showing the geographic distribution of assets and people at risk (section one), hazards assessed (section two) and potential monetary losses and casualties (section three). The profiles also include an analysis of the possible direct losses (in absolute terms and normalized by GDP) caused by tropical cyclones and earthquakes, and their impact though severe winds, rainfall, coastal storm surge, ground shaking and tsunami waves. The expected return period indicates the likelihood of a certain specified loss amount to be exceeded in any one year.

Africa's growing demand for food has been met increasingly by imports from the global market. This, coupled with rising global food prices, brings ever-mounting food import bills. In addition, population growth and changing demand patterns will double demands over the next 10 years. Two key issues must be addressed: (a) establishing a consistent and stable policy environment for regional trade in fertilizers; and (b) investing in institutions that reduce the transaction costs of coordination failures. Many countries have enacted new fertilizer laws in recent years, but few have provided the resources to define and enforce regulations through standards and testing capacity. This report shows that reducing regulatory burdens on fertilizers and the consequent increase in use of fertilizers will have substantial impacts on returns to farmers, with consequent impacts on poverty. The report highlights the range of barriers to food trade in Africa along the entire value chain. The issues pertain to many ministries and agencies within government: trade, agricultural, health and safety, transport, and finance. This in turn requires a "whole of government' approach to freeing up food trade, which will require strong and effective leadership to articulate the rationale and sustain the momentum for reform. Leaders must also address the hard choices that will arise in dealing with the political economy constraints that have until now blocked the capacity of Africa to exploit its enormous potential to feed Africans.

Potato starch was hydrolyzed with HCI to obtain starch with different molecular weights. Different concentrations of acrylamide were grafted onto hydrolyzed starches in the presence of potassium permanganate/citric acid as an initiator. The newly synthesized products were used as sizing agents of cotton yams to test their suitability for temporary improvement of physico-mechanical properties. With the increase of the potassium permanganate concentration the graft yield of copolymerization increased and then drop off ; (b) increased by increasing the acrylamide concentration within the range studied. The molecular weights of copolymers were investigated by high-performance liquid chromatography (HPLC). Mean molar mass and molar mass distributions were determined by gel permeability chromatography Agilent 1100 Series GPC where the detector is used as a differential refractometer (RID detector) 1200 Series. After chromatography of an appropriate sample of copolymer, depending on the used detector (RID or DAD), ChemStation software depending (RID or DAD) provides the corresponding chromatograms with typical chromatographic parameters. The program enables the activation of GPC software and transfer data obtained chromatograms for processing and analysis of molecular weight of each separated fraction of the analyzed polymers. It was found that the molecular weight of the grafted starch directly affects the rheology and the behavior of the solution (sizing agent), the efficiency of the process of sizing the yarn and then the safety and reliability of the process of weaving. On the other hand, physico-mechanical properties of cotton textiles, such as tensile strength, elongation at break and abrasion resistance, were found to be highly enhanced with the copolymers derived from hydrolyzed starches used as size base materials: while worse textile properties were found when the original starch was used as a sizing agent.

"Members of the genus Dioscorea, food yams, were introduced to Jamaica from Africa during the slave era and have remained a staple in local diets and national cuisine. Yam cultivation has also been an important economic activity providing employment for thousands of rural Jamaicans. Until the 1960s yams were grown for local use by subsistence growers for home consumption or by commercial growers for sale in local produce markets. Since then, however, yam has also grown to become an important export crop. With its value added potential virtually untouched, this crop possesses intriguing possibilities from the standpoint of food security and rural livelihoods in yam growing areas of Jamaica. At the same time there are concerns about the ecological and economic sustainability of yam farming under current conditions. In this paper we will analyze the sustainability of yam cultivation and consider concrete strategies for increasing the environmental sustainability and enhancing its contribution to food security."

Made available in DSpace on 2014-06-11T19:26:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-18Bitstream added on 2014-06-13T20:55:01Z : No. of bitstreams: 1 ferreira_ab_me_botfca.pdf: 1827601 bytes, checksum: b017d5489f44eb1c042dcabf9e93e729 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) As dioscoreáceas constituem uma importante fonte alimentar e estão distribuídas nas regiões tropicais, subtropicais e temperadas de todo mundo. O gênero Dioscorea, ao qual pertence a maioria das espécies cultivadas e silvestres da família, engloba espécies tropicais originárias da África, Ásia e América. O objetivo do trabalho foi realizar um levantamento das variedades de cará (Dioscorea spp.) cultivadas pelos agricultores com o intuito de verificar as espécies mantidas por eles e suas diversidades, nomes populares das variedades e sobre o sistema produtivo da cultura como: preparo das túberas sementes, manejo da cultura, preparo do solo, plantio, tratos culturais e comercialização. Para o início da pesquisa de campo, foi usada a técnica de amostragem do tipo “bola de neve”, que consistiu em conversar com alguns agricultores e vendedores dos mercados de hortaliças da região para a localização dos principais agricultores que cultivam o cará e suas indicações subsequentes. Durante a pesquisa de campo, foram encontrados 48 agricultores que cultivam diversas culturas e também plantam o cará, com seu respectivos nomes populares para o gênero. Foram encontradas três espécies: Dioscorea alata, D. trifida e D. bulbifera. O preparo do solo é feito de forma rudimentar e o cultivo do cará é feito no sistema de “roça de toco”. 14% dos agricultores utilizaram algum tipo de implemento agrícola para o preparo do solo. O preparo das “sementes” varia de acordo com cada espécie, sendo que 55% são plantadas partidas e 45% inteiras. A organização e destino da produção acontecem nas comunidades, onde grande parte é destinada à alimentação familiar, e o excedente é para a venda direta para consumidores ou via intermediários The dioscoreaceas constitute an important source of food and are distributed in tropical, subtropical and temperate all over the world. The genus Dioscorea, whose the most cultivated and wild species of the family belong to, encompassing tropical species originally from Africa, Asia and America. The objective was to survey the varieties of yams grown by farmers in order to verify the species kept by them and their diversity, popular names of the varieties and the crop production system as: preparation of tubers-seeds, crop management, soil preparation, planting, cultivation and marketing. In the field research the sampling snowball, was used, which consisted of talking to some farmers and vegetable sellers in the region for the location of the main farmers who grow yams. During the fieldwork, there were 48 farmers growing different crops and also plant the yams, their respective common names for the genus. Three species were found: Dioscorea alata, D. trifida and D. bulbifera. Soil preparation is done rudimentary and the cultivation of yams is done on a “slash and burn” system. 14% of farmers used some type of agricultural implement for soil tillage. The “seed” preparation varies with each species, 55% are planted using divided portions of the tubers and 45% using entire tubers. The organization of production and destination are done in communities where a large part is devoted to the family diet, and the surplus is for sale delivered directly to consumers or by middle-men

The study evaluated the economics of seed yam production using the minisett technique in Oyo State, South West Nigeria. The analysis was based on input and output data collected from sixty yam (Dioscorea spp.) farmers and the existing market price in the area. The socio-economic characteristics of the respondents were analyzed using descriptive statistics. The structure of production costs was analyzed using percentages while gross margin analysis was used to determine the profitability of seed yam production using the minisett technique. Results of the analysis showed that seed yam production was dominated by men. The farmers had an average household size of 7.7 with a median of 7.0 and a mode of 7. Most of them were educated and had other occupations. The farmers assessed the technique as good, very good or excellent. The revenue per hectare of seed yam production was N337, 500. The total cost of production was N150,500 while the cost per seed yam was N16.72. On every naira invested in seed yam production using the minisett technique, farmers were expected to have N1.24 net returns. This shows that seed yam production using the minisett technique was a profitable venture in the study area. Labour costs alone accounted for 78.1% of the production cost. There is hence a need to deploy appropriate technologies to reduce these costs as a means of further reducing production costs and increasing the profitability of seed yams production using the minisett technique. L’étude portait sur l’évaluation de l’économie de la production de semences d’igname à l’aide de la technique des minisetts dans l’Etat d’Oyo, au sud-ouest du Nigéria. L’analyse était fondée sur les données d’entrée et de sortie recueillies auprès de soixante producteurs d’ignames (Dioscorea spp.) et sur les prix de marché actuels dans la région. Les caractéristiques socio-économiques des personnes interrogées ont été analysées à l’aide de statistiques descriptives. La structure des coûts de production a été analysée à l’aide de pourcentages, tandis que l’analyse de la marge brute a permis de déterminer la rentabilité de la production de semences d’ignames à l’aide de la technique des minisetts. Les résultats de cette analyse ont montré que la production de semences d’ignames était dominée par les hommes. Chez les producteurs, la taille moyenne du ménage était de 7,7 personnes, la taille médiane de 7,0 personnes et la taille modale de 7 personnes. La plupart des producteurs étaient instruits et avaient d’autres métiers. Les producteurs ont évalué la technique comme bonne, très bonne ou excellente. Le revenu par hectare de production de semences d’igname s’élevait à 337 500 N. Le coût total de production était de 150 500 N tandis que le coût par semence d’igname s’élevait à 16,72 N. Pour chaque naira investi dans la production de semences d’igname utilisant la technique des minisetts, les producteurs sont donc censés obtenir un revenu net de 1,24 N. Cela montre que la production de semences d’igname à l’aide de la technique des minisetts était une activité rentable dans la région couverte par l’étude. Les coûts de main-d’œuvre représentaient à eux seuls 78,1 % du coût total de production. Il est donc nécessaire de déployer les techniques appropriées pour réduire ces coûts, et ainsi réduire les coûts de production et accroître la rentabilité de la production de semences d’igname à l’aide de la technique des minisetts. El estudio evalúa la economía de la producción de semilla de ñame usando la tecnología «minisett» en el Estado de Oyo, al sudeste de Nigeria. El análisis se basa en los datos de entrada y salida recabados a partir de sesenta cultivadores de ñame (Dioscorea spp.) y del precio de mercado existente en la zona. Las características socioeconómicas de los participantes en el estudio se analizan mediante la estadística descriptiva. La estructura de costes de producción se analiza usando porcentajes, mientras que el análisis del margen bruto se usa para determinar la rentabilidad de la producción de semilla de ñame con la técnica «minisett». Los resultados del análisis muestran que la producción de semilla de ñame está dominada por hombres. Los cultivadores pertenecen a una unidad familiar de un tamaño medio de 7,7, con una mediana de 7,0 y una moda de 7. La mayoría están educados y tienen otras ocupaciones. Los cultivadores calificaron la técnica como buena, muy buena o excelente. Los ingresos por hectárea de producción de semilla de ñame fueron de 337,500 N. El coste total de la producción fue de 150,500 N, mientras que el coste por semilla de ñame fue de 16,72 N. Por cada naira invertida en la producción de semilla de ñame mediante la técnica «minisett», los cultivadores prevén obtener un beneficio neto de 1,24 N. Esto demuestra que la producción de semilla de ñame mediante la técnica «minisett» es una empresa rentable en la zona de estudio. Los costes de mano de obra por sí solos suponen el 78,1% de los costes de producción. Por lo tanto, es necesario desplegar las tecnologías apropiadas para reducir dichos costes a fin de reducir aun más los costes de producción y aumentar la rentabilidad de la producción de semilla de ñame mediante la técnica «minisett».

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; 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.

The study evaluated the economics of seed yam production using the minisett technique in Oyo State, South West Nigeria. The analysis was based on input and output data collected from sixty yam (Dioscorea spp.) farmers and the existing market price in the area. The socio-economic characteristics of the respondents were analyzed using descriptive statistics. The structure of production costs was analyzed using percentages while gross margin analysis was used to determine the profitability of seed yam production using the minisett technique. Results of the analysis showed that seed yam production was dominated by men. The farmers had an average household size of 7.7 with a median of 7.0 and a mode of 7. Most of them were educated and had other occupations. The farmers assessed the technique as good, very good or excellent. The revenue per hectare of seed yam production was N337, 500. The total cost of production was N150,500 while the cost per seed yam was N16.72. On every naira invested in seed yam production using the minisett technique, farmers were expected to have N1.24 net returns. This shows that seed yam production using the minisett technique was a profitable venture in the study area. Labour costs alone accounted for 78.1% of the production cost. There is hence a need to deploy appropriate technologies to reduce these costs as a means of further reducing production costs and increasing the profitability of seed yams production using the minisett technique.L’étude portait sur l’évaluation de l’économie de la production de semences d’igname à l’aide de la technique des minisetts dans l’Etat d’Oyo, au sud-ouest du Nigéria. L’analyse était fondée sur les données d’entrée et de sortie recueillies auprès de soixante producteurs d’ignames (Dioscorea spp.) et sur les prix de marché actuels dans la région. Les caractéristiques socio-économiques des personnes interrogées ont été analysées à l’aide de statistiques descriptives. La structure des coûts de production a été analysée à l’aide de pourcentages, tandis que l’analyse de la marge brute a permis de déterminer la rentabilité de la production de semences d’ignames à l’aide de la technique des minisetts. Les résultats de cette analyse ont montré que la production de semences d’ignames était dominée par les hommes. Chez les producteurs, la taille moyenne du ménage était de 7,7 personnes, la taille médiane de 7,0 personnes et la taille modale de 7 personnes. La plupart des producteurs étaient instruits et avaient d’autres métiers. Les producteurs ont évalué la technique comme bonne, très bonne ou excellente. Le revenu par hectare de production de semences d’igname s’élevait à 337 500 N. Le coût total de production était de 150 500 N tandis que le coût par semence d’igname s’élevait à 16,72 N. Pour chaque naira investi dans la production de semences d’igname utilisant la technique des minisetts, les producteurs sont donc censés obtenir un revenu net de 1,24 N. Cela montre que la production de semences d’igname à l’aide de la technique des minisetts était une activité rentable dans la région couverte par l’étude. Les coûts de main-d’œuvre représentaient à eux seuls 78,1 % du coût total de production. Il est donc nécessaire de déployer les techniques appropriées pour réduire ces coûts, et ainsi réduire les coûts de production et accroître la rentabilité de la production de semences d’igname à l’aide de la technique des minisetts.El estudio evalúa la economía de la producción de semilla de ñame usando la tecnología «minisett» en el Estado de Oyo, al sudeste de Nigeria. El análisis se basa en los datos de entrada y salida recabados a partir de sesenta cultivadores de ñame (Dioscorea spp.) y del precio de mercado existente en la zona. Las características socioeconómicas de los participantes en el estudio se analizan mediante la estadística descriptiva. La estructura de costes de producción se analiza usando porcentajes, mientras que el análisis del margen bruto se usa para determinar la rentabilidad de la producción de semilla de ñame con la técnica «minisett». Los resultados del análisis muestran que la producción de semilla de ñame está dominada por hombres. Los cultivadores pertenecen a una unidad familiar de un tamaño medio de 7,7, con una mediana de 7,0 y una moda de 7. La mayoría están educados y tienen otras ocupaciones. Los cultivadores calificaron la técnica como buena, muy buena o excelente. Los ingresos por hectárea de producción de semilla de ñame fueron de 337,500 N. El coste total de la producción fue de 150,500 N, mientras que el coste por semilla de ñame fue de 16,72 N. Por cada naira invertida en la producción de semilla de ñame mediante la técnica «minisett», los cultivadores prevén obtener un beneficio neto de 1,24 N. Esto demuestra que la producción de semilla de ñame mediante la técnica «minisett» es una empresa rentable en la zona de estudio. Los costes de mano de obra por sí solos suponen el 78,1% de los costes de producción. Por lo tanto, es necesario desplegar las tecnologías apropiadas para reducir dichos costes a fin de reducir aun más los costes de producción y aumentar la rentabilidad de la producción de semilla de ñame mediante la técnica «minisett».

This report is the final product of a country case study prepared in the framework of the comparative analysis of organization and performance of cotton sectors in Sub-Saharan Africa, a study published by the World Bank in 2008. The objective of the overall study was to carry out a comparative analysis of the links between sector structure and observed performance outcomes on a sample of nine of the major cotton exporting countries of Sub-Saharan Africa, and draw lessons from each country's experience that can provide useful guidance to policy-makers, industry stakeholders, and interested donors agencies in the design of future cotton sector reform programs. This paper describes and reviews the situation of the cotton sector of Cote d'Ivoire, as well as the reforms that the sector has undergone since the mid-1990s.

Coffee is an ecologically and economically significant crop for Haiti. It is not only the main source of income for more than 100,000 farmers, but the coffee ecosystem also sustains a large part of the remaining tree cover (currently at less than 1.5 percent of land) of the country. This report does not aim to detail the structural constraints impacting upon the Haitian coffee sub-sector. Instead, it describes the risks affecting the existing supply chain in terms of their potential impact and prioritizes the risks and areas requiring attention for risk management, investment, and capacity building. The Haitian coffee industry is constrained by significant systemic problems which have contributed to its decline over the years. Some of these major constraints include: (1) the structure of the coffee creole garden which contributes to low on-farm coffee productivity; (2) a land tenure system which inhibits long term investment; (3) poor transportation and logistics infrastructure; (4) limited access to credit and high interest rates; (5) aging coffee trees and farmers; (6) waning government interest and support for the coffee sub-sector; (7) lack of industry level coordination; and (8) a lack of international and domestic promotion of the Haitian coffee industry.

International audience; This paper describes a part of the men's responsibilities, both agricultural and ritual, in Wallis Island, Western Polynesia. Yams are the main focus of this study including agricultural techniques, indigenous classifications, ritual system and exchange pathways. It shows that yams are involved in a large system of relationships that defines everything in relation with the society itself. Comparable to sons that men would get from their gardens, these tuber partake, by circulating in exchanges, in the differentiated constitution of living people, the world's renewing and the society's everlastingness.; Cet article, qui présente le travail horticole et une partie des responsabilités rituelles des hommes à Wallis (Polynésie occidentale), porte sur les ignames (mise en culture, classifications indigènes, système rituel et circuits d'échange) et montre que ces tubercules participent d'un vaste système de relations qui définissent tout être en référence à la société wallisienne dont le " roi " scelle l'ensemble de l'organisation. Comparables à des enfants masculins que les hommes obtiennent de leurs jardins, les ignames concourent, en circulant dans les échanges, à la constitution différenciée des vivants, au renouvellement du monde et à la pérennisation de la société.

International audience; Tropical root and tuber crops are staple foods in developing countries where they are the main source of carbohydrates and a potential source of secondary metabolites such as carotenoids. Enhancing carotenoid content has considerable potential for improving human nutrition in these areas. Except for cassava and sweet potato, carotenoid content has not been evaluated in large germplasm collections. We describe a simple HPLC-DAD-based protocol for the reliable characterization of carotenoids in root crops. Less than 5% variation in carotenoid content was found among samples collected from tubers of the same plant or from clones of the same genotype. Carotenoids were evaluated in 153 accessions representing 10 different species. Each species had a specific profile of carotenoids, and accessions of the same species differed greatly in their individual content. The database assembled during this study represents a useful tool for nutritionists and breeders working on biofortification of root crops with carotenoids.

This paper uses new data on agricultural policy interventions to examine the political economy of agricultural trade policies in Sub-Saharan Africa. Historically, African governments have discriminated against agricultural producers in general (relative to producers in non-agricultural sectors), and against producers of export agriculture in particular. While more moderate in recent years, these patterns of discrimination persist. They do so even though farmers comprise a political majority. Rather than claiming the existence of a single best approach to the analysis of policy choice, the authors explore the impact of three factors: institutions, regional inequality, and tax revenue-generation. The authors find that agricultural taxation increases with the rural population share in the absence of electoral party competition; yet, the existence of party competition turns the lobbying disadvantage of the rural majority into political advantage. The authors also find that privileged cash crop regions are particular targets for redistributive taxation, unless the country's president comes from that region. In addition, governments of resource-rich countries, while continuing to tax export producers, reduce their taxation of food consumers.