Search

Dans un monde confronté aux changements climatiques et à des pandémies en lien avec la destruction des milieux naturels, les enjeux liés à la préservation de la biodiversité sont dorénavant bien connus et ont donné lieu à des accords internationaux majeurs, comme le protocole de Nagoya. Dans ce contexte mondial, les recherches menées au Sud sont primordiales. Les contributions rédigées ici par des chercheurs dʼAfrique, de lʼocéan Indien, dʼAsie du Sud-Est et dʼEurope traduisent la vigueur de la recherche sur la biodiversité dans les pays intertropicaux francophones. Documenter la diversité des écosystèmes végétaux locaux, mieux connaître les savoirs traditionnels et les utilisations populaires des plantes ou des champignons, valoriser le rôle des collections botaniques, identifier des chaînes de valorisation économique responsables, gérer durablement les écosystèmes et leurs ressources, élaborer des outils stratégiques pour une gouvernance environnementale basée sur la science et, enfin, montrer la nécessité de lʼimplication citoyenne et de lʼensemble des acteurs concernés, tels sont les grands thèmes déclinés ici. Cet ouvrage collectif intéressera tous ceux qui travaillent sur la biodiversité des écosystèmes intertropicaux. Il souligne la nécessité dʼune science de lʼaction au service du développement durable.

Graines pour préparations médicales sur le marché de Kpalimé, Togo. © IRD/C. Brun « Valoriser la biodiversité » revêt une signification différente selon le contexte dans lequel cette notion est employée, mais également selon le profil de chacun. Communément, il s’agit d’ajouter de la valeur à une ressource, à un ensemble de ressources, ou à un écosystème entier, au travers de diverses activités dont la recherche, et qui s’accompagnent d’une évaluation multicritère. Par habitude, cette action...

Introduction Les végétaux jouent un rôle important pour la survie de l’humanité par leur capacité à synthétiser un grand nombre de molécules organiques complexes quelquefois pourvues d’activités biologiques. Les échanges commerciaux entre pays ont donné lieu à une large et peu contrôlée utilisation de la biodiversité (Kpètèhoto et al., 2017). Certains acteurs s’approprient ainsi illégalement non seulement des ressources biologiques mais également les connaissances traditionnelles des peuples ...

Dans un monde confronté aux changements climatiques et à des pandémies en lien avec la destruction des milieux naturels, les enjeux liés à la préservation de la biodiversité sont dorénavant bien connus et ont donné lieu à des accords internationaux majeurs, comme le protocole de Nagoya. Dans ce contexte mondial, les recherches menées au Sud sont primordiales. Les contributions rédigées ici par des chercheurs dʼAfrique, de lʼocéan Indien, dʼAsie du Sud-Est et dʼEurope traduisent la vigueur de la recherche sur la biodiversité dans les pays intertropicaux francophones. Documenter la diversité des écosystèmes végétaux locaux, mieux connaître les savoirs traditionnels et les utilisations populaires des plantes ou des champignons, valoriser le rôle des collections botaniques, mais aussi identifier des chaînes de valorisation économique responsables, gérer durablement les écosystèmes et leurs ressources, élaborer des outils stratégiques pour une gouvernance environnementale basée sur la science et, enfin, montrer la nécessité de lʼimplication citoyenne et de lʼensemble des acteurs concernés, tels sont les grands thèmes déclinés ici. Cet ouvrage collectif intéressera tous ceux qui travaillent sur la biodiversité des écosystèmes intertropicaux. Il souligne la nécessité dʼune science de lʼaction au service du développement durable.

Crop diversity represents a major resource for sustainable agriculture. They are at the nexus of important societal and economic issues that involve a wide range of actors (farmers, breeders,researchers) who do not necessarily share the same objectives but yet are interdependent with regard to their access to diversity, either locally or even globally. In this context, there is a growing need to engage all stakeholders on their exchange practices: modalities of access to, and use of genetic resources and associated knowledge, and of benefit-sharing. With the objective of building a common vision of equitable exchange practices and partnership rules within the framework of the ITPGRFA and the Nagoya Protocol, we chose a singular medium: the forum theatre. This form of participatory theatre was specifically designed for discussing issues related to power relationships. In this sense, the play brings the audience to discuss choices made and action taken by various characters and their relationships. It also offers the opportunity to interact directly by proposing actions to alleviate tensions between parties. A script was built by researchers from different disciplines and presented in different contexts: (i) as part of a multi-stakeholder workshop bringing together public researchers, breeders and representatives of civil society from West Africa; (ii) during regional and national peasant seeds fairs, in Senegal that gathered producers, peasant organizations, associations and NGOs. By performing the play in front of different audiences, multiples points of view were expressed. The forum theatre allowed (i) to open public spaces for discussion about plant genetic resources management, (ii) to collectively identify and experiment different ways of improving collaborative practices and (iii) to contribute in the formalization of a charter for increased fairness in collaboration among the diversity of stakeholders involved.

Oryza sativa rice has been domesticated in Asia and has moved into Africa by various routes for over a millennium. Cultivars may have undergone a particular evolution during and after their migration, leading to novel adaptations. Making use of the resequencing data available in the 3000 Rice Genomes data set (Wang et al 2018), we applied a method recently developed (Santos et al., 2019) in order to relate the genetic diversity of this species between Africa and Asia. We used data from 1252 accessions, including all 249 accessions from Africa and 1003 landraces from Asia, characterised with over 10 million high quality SNPs. Our pipeline relies on Principal Component Analysis (PCA) for dimension reduction and on Kernel Density Estimation for discriminant analysis and classification of local genome segments. Local haplotypes are described in relation to Indica, Japonica and cAus references. This step is complemented by an analysis of local clusters for deeper exploration. We analysed over a hundred thousand overlapping windows of 150 SNPs. Summary analyses of local classification by genome and physical position allowed us to identify ambiguities between groups, which are possible signals of genetic exchange. Browsing through the genome, we detected potential introgressions between the different rice sub-populations and were able to isolate those specific to African accessions. We selected several on chromosome 6, corresponding to large (over 100 kb) segments of the Indica type or the cAus type observed in upland rice varieties globally classified as Japonica. We used these signals to start a systematic inventory of discrete introgressions in the rice genome and investigate their value to trace back the history of broad migrations and patterns of adaptation. Diversity in introgression-free genome portions indicates that African upland rice derives from Asian tropical Japonica rice with a significant decrease in diversity along the migration.

Modern rice cultivars are adapted to a range of environmental conditions and human preferences. At the root of this diversity is a marked genetic structure, owing to multiple foundation events. Admixture and recurrent introgression from wild sources have played upon this base to produce the myriad adaptations existing today. Genome-wide studies bring support to this idea, but understanding the history and nature of particular genetic adaptations requires the identification of specific patterns of genetic exchange. In this study, we explore the patterns of haplotype similarity along the genomes of a subset of rice cultivars available in the 3,000 Rice Genomes data set. We begin by establishing a custom method of classification based on a combination of dimensionality reduction and kernel density estimation. Through simulations, the behavior of this classifier is studied under scenarios of varying genetic divergence, admixture, and alien introgression. Finally, the method is applied to local haplotypes along the genome of a Core set of Asian Landraces. Taking the Japonica, Indica, and cAus groups as references, we find evidence of reciprocal introgressions covering 2.6% of reference genomes on average. Structured signals of introgression among reference accessions are discussed. We extend the analysis to elucidate the genetic structure of the group circum-Basmati: we delimit regions of Japonica, cAus, and Indica origin, as well as regions outlier to these groups (13% on average). Finally, the approach used highlights regions of partial to complete loss of structure that can be attributed to selective pressures during domestication.

The FAO recently estimated that demand for food would increase by 70% by 2050. The challenge will not only be on increasing the food supply, but also on improving its nutritional value. Until now, despite the call for an increased use of underutilized crops to diversify alimentation and provide sustainable agriculture, those crops remain a largely untapped reservoir of agrobiodiversity. Are they really crops for the future? In this regard, fonio (Digitaria exilis Stapf) appears as a promising crop. It is an indigenous staple cereal from Western Africa regarded as a valuable source of income, especially for small-scale farmers. It plays a crucial role in food and nutrition security: short length cycles varieties can be harvested during the shortage season. Nevertheless, fonio remains largely under-studied compared to other African cereals such as sorghum or millet. The need to characterize its genetic resources and adaptive potential to the fast-evolving environmental pressures is therefore crucial. Herein, we assess the genetic diversity of fonio and its evolutionary history at both regional and local scale. We show that genetic diversity is highly linked to geographic origin, ethnic groups and climate conditions. We discuss the implication in terms of domestication history and conservation.

Introgression among rice populations is worth studying for its role as a path to adaptation. Along human migrations, gene flow between cultivars and wild or primitive cultivated forms have generated new types which thus harbor admixed genomes with distinct components traceable to early crop history. Recent analyses based on massive sequencing efforts have enabled detailed studies of crop evolution in rice that revealed introgressions allowing the spread of domestication factors across varietal groups as well as the secondary hybrid origin of some varietal clusters. Yet distinct views still coexist as to the global interpretation of the data, featuring one vs multiple domestication events and diverse scenarios for the origin of secondary varietal groups. Contrasting hypotheses make it difficult to draw conclusions from the data given their weight on the premises underlying any analysis. Nonetheless, by recognizing the existence of more or less cohesive groups of rice varieties, important information can still be extracted as to their interactions. The results presented here are a still frame of our analysis of the exchanges between the major clusters of rice genetic diversity, Japonica, Indica and circumAus, as can be determined by their relative differentiation, and the concomitant retrieval of the cryptic circumBasmati genetic signature.