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Kankan, Guinea

Sagnard F.,CIRAD - Agricultural Research for Development | Sagnard F.,co ILRI | Deu M.,CIRAD - Agricultural Research for Development | Dembele D.,ICRISAT | And 9 more authors.
Theoretical and Applied Genetics

Gene flow between domesticated plants and their wild relatives is one of the major evolutionary processes acting to shape their structure of genetic diversity. Earlier literature, in the 1970s, reported on the interfertility and the sympatry of wild, weedy and cultivated sorghum belonging to the species Sorghum bicolor in most regions of sub-Saharan Africa. However, only a few recent surveys have addressed the geographical and ecological distribution of sorghum wild relatives and their genetic structure. These features are poorly documented, especially in western Africa, a centre of diversity for this crop. We report here on an exhaustive in situ collection of wild, weedy and cultivated sorghum assembled in Mali and in Guinea. The extent and pattern of genetic diversity were assessed with 15 SSRs within the cultivated pool (455 accessions), the wild pool (91 wild and weedy forms) and between them. F ST and R ST statistics, distance-based trees, Bayesian clustering methods, as well as isolation by distance models, were used to infer evolutionary relationships within the wild-weedy-crop complex. Firstly, our analyses highlighted a strong racial structure of genetic diversity within cultivated sorghum (F ST = 0.40). Secondly, clustering analyses highlighted the introgressed nature of most of the wild and weedy sorghum and grouped them into two eco-geographical groups. Such closeness between wild and crop sorghum could be the result of both sorghum's domestication history and preferential post-domestication crop-to-wild gene flow enhanced by farmers' practices. Finally, isolation by distance analyses showed strong spatial genetic structure within each pool, due to spatially limited dispersal, and suggested consequent gene flow between the wild and the crop pools, also supported by R ST analyses. Our findings thus revealed important features for the collection, conservation and biosafety of domesticated and wild sorghum in their centre of diversity. © 2011 Springer-Verlag. Source

Vayssieres J.-F.,CIRAD - Agricultural Research for Development | Vayssieres J.-F.,Biol Control Unit Afr | Sinzogan A.,University Abomey Calavi | Adandonon A.,University of Benin | And 22 more authors.

Introduction: Losses in West African commercial mango orchards due to fruit fly infestations have exceeded 50% by the middle of the crop season since 2005, resulting in considerable income loss for the growers. Materials and methods: In 2009, weekly monitoring of adult fruit fly species of economic significance was carried out in eight West African countries at 12 sites across five agro-ecological zones: (i) Humid Forest, (ii) Guinean savanna, (iii) Southern Sudan, (iv) Northern Sudan, and (v) Sahelian. Trapping was performed using methyl eugenol and terpinyl acetate in 288 Tephri-traps, targeting Bactrocera invadens and Ceratitis cosyra. Results: The data showed that B. invadens was present throughout the year in the Forest zone, abundant for 7 months, with a peak in May at the end of the mango season, C. cosyra being totally absent. In the Guinean savanna zone, B. invadens was abundant for 6-7 months, with a peak at the beginning of June coinciding with the season, with a few C. cosyra. In the Southern Sudan zone, B. invadens was abundant for 6 months, with a peak in mid-June during the season, C. cosyra peaking in April. In the Northern Sudan zone, B. invadens was abundant for 5 months, with a peak at the end of June at the end of the season, C. cosyra peaking in May. In the Sahelian zone, B. invadens was abundant for 4 months, peaking in August during the season, C. cosyra peaking just before. These preliminary results showed that the exotic species, B. invadens, was present at high levels [mean peak of 378 flies per trap per day (FTD)] in all agro-ecological zones, while the native species, C. cosyra, preferred the drier zones of West Africa, with lower population levels (mean peak of 77 FTD). Conclusion: Detection trapping of male flies with parapheromones is a useful indicator of field population levels and could be used to deploy control measures (IPM package) in a timely manner when the Economic Injury Level is reached. Control strategies for these quarantine mango fruit fly species are discussed with respect to agro-ecological zones and the phenological stages of the mango tree. © 2014 Cirad/EDP Sciences. Source

Correia M.,CIRAD - Agricultural Research for Development | Diabate M.,IRAG | Beavogui P.,IRAG | Guilavogui K.,IRAG | And 2 more authors.
Biodiversity and Conservation

In the current deforestation context, agroforestry is increasingly considered in the tropical zone for its potential contribution to biodiversity conservation. In Guinée Forestière (Guinea, West Africa), coffee-based species rich agroforests are currently expanding on agricultural land around most villages. To assess the role these agroforests play with respect to biodiversity conservation, we compared their tree structure and diversity with those of a neighbouring natural forest. Eighty plots were sampled using a variable area transect method (60 plots distributed into 3 village agroforests, 20 natural forest plots). The structure of coffee-based agroforests showed obvious signs of farmers' management: density of mature trees was significantly lower than in natural forest and most juvenile trees were eliminated and replaced by coffee trees. However, tree seedling density was not significantly different than in natural forest. Tree species richness and diversity were also lower than in natural forest but much higher than in any other agricultural or agroforestry land use system. These results are close to those obtained in the coffee-based agroforests of Central America, confirming that coffee-based agroforests retain many forest species that play a key role in the conservation of regional forest tree diversity. © 2010 Springer Science+Business Media B.V. Source

Barnaud A.,IRD Montpellier | Vigouroux Y.,IRD Montpellier | Billot C.,CIRAD - Agricultural Research for Development | Noyer J.-L.,CIRAD - Agricultural Research for Development | And 5 more authors.
Acta Horticulturae

Underutilized crops do not benefit from the same research effort as major crops even if they are locally essential for food security. Knowledge and resources developed on major crops could be transferred to the lesser studied ones in order to analyze and exploit the genetic and agronomical potential of these crops. Fonio, so-called by farmers and consumers, includes Digitaria exilis Stapf, and D. iburua Stapf, as well as wild related species (D. ternata and D. longiflora) and Bmchiaria or Panicum genera. It is an indigenous staple crop in western Africa regarded as a valuable source of income, especially for small scale farmers. Recent progress in post-harvest technologies, which has long hampered the development of fonio cultivation, has increased its economic potential. The need to characterize its genetic resources and adaptive potential to the changing climate, and more generally, fast evolving environmental pressures, is therefore more important. We shall discuss how the study, conservation and uses of fonio genetic resources can take advantage of methodological advances in other plant genetic research. Several issues are addressed, which are not only related to biotechnologies but also to the combination of biological and social science approaches. The genetic structure of crop on-farm diversity results from the interplay between numerous factors, including historical, social, cultural, economic, biological and environmental factors. Molecular resources can now be developed rapidly. Combined with innovative and multidisciplinary approaches, this will lead to an accurate estimation of fonio evolutionary history (including domestication), as well as an evaluation of the genetic resources and their dynamics. These approaches will allow a better understanding of on-farm diversity of fonio, the development of sound collecting and ex situ conservation strategies and appropriate crop improvement to ensure food security. Source

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