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The future of R&I as driver of agrifood system transformation and sustainability transitions in fragile contexts. Perspectives from Burkina Faso
Get PDFHélioSPIR. Résumés des communications présentées aux 26èmes rencontres HélioSPIR, Montpellier (France), 24-25 juin 2025
Get PDFReconstructing the silent circulation of West Nile Virus in a Caribbean island during 15 years using sentinel serological data
Get PDFThe dynamics of zoonotic infectious diseases with silent circulation may be imperfectly understood and monitored using passive (or reactive) epidemiological surveillance data only, highlighting the interest of quantitative methods like modelling. West Nile virus (WNV) is a widespread mosquito-borne virus transmitted from birds to “dead-end” hosts including humans and horses, in whom it can be fatal. It was first detected in Guadeloupe, Caribbean, in 2002, although no WNV clinical case in humans nor horses had been reported on the archipelago before 2024. Undetected infections represent a risk as WNV can be transmitted via blood and organ donations. In Guadeloupe, epidemiological surveillance started in 2002 in chickens and horses and in 2015 in mosquitoes, to detect WNV and to improve knowledge on its epidemiology and dynamics. In order to reconstruct the WNV force of infection (FOI), we built a model assessing different hypotheses regarding its dynamics using serological results in respectively 1,022 and 3,649 blood samples collected from 256 horses and 317 chickens between 2002 and 2018. We fitted the model to the serological data using a Markov Chain Monte Carlo algorithm. We found that WNV FOI in Guadeloupe Island presented both within-year (seasonal) and between-years fluctuations. We identified three main episodes of WNV circulation on the island between 2002 and 2017. During years with circulation, the FOI was predicted to be highest around the months of October-November, although transmission could occur all year long. We estimated a very low weekly seroreversion rate, which is consistent with a lifelong persistence of WNV IgG antibodies in many infected individuals. To conclude, combining longitudinal serological data to a mathematical model allowed reconstructing the recurrent and silent circulation of WNV in this Caribbean island, which could improve surveillance design for better virus detection
Evaluation of two candidate molecules - TCTP and cecropin - on the establishment of Trypanosoma brucei gambiense into the gut of Glossina palpalis gambiensis
Get PDFTrypanosomiasis, transmitted by tsetse flies (Glossina spp.), poses a significant health threat in 36 sub-Saharan African countries. Current control methods targeting tsetse flies, while effective, allow reinfestation. This study investigates paratransgenesis, a novel strategy to engineer symbiotic bacteria in tsetse flies, Sodalis glossinidius, to deliver anti-trypanosome compounds. Disrupting the trypanosome life cycle within the fly and reducing parasite transmission could offer a sustainable solution for trypanosomiasis control. In this context, we tested the effect of cecropin, reported to be lethal for Trypanosoma cruzi (Chagas disease) and TbgTCTP (Translationally Controlled Tumor Protein from Trypanosoma brucei gambiense), previously reported to modulate the growth of bacteria isolated from the fly microbiome, to delay the first peak of parasitemia and the death of trypanosome-infected mice. We have successfully cloned and transfected the genes encoding the two proteins into Sodalis strains. These Sodalis recombinant strains (recSodalisTbgTCTP and recSodaliscecropin) have been then microinjected into the L3 larval stage of Glossina palpalis gambiensis flies. The stability of the cloned genes was checked up to the 20th day after microinjection of recSodalis. The rate of fly emergence from untreated pupae was 95%; it was reduced by nearly 50% due to the mechanical injury caused by microinjection. It decreased to nearly 7% when larvae were injected with recSodalisTbgTCTP, which suggests TCTP could have a lethal impact to larvae development. When challenged with T. brucei gambiense, a slightly lower, but statistically non-significant, infection rate was recorded in flies harboring recSodaliscecropin compared to control flies. The effect of recSodalisTbgTCTP could not be measured due to the very low rate of fly emergence after corresponding treatment of the larvae. The results do not allow to conclude on the effect of cecropin or TCTP, delivered by para-transgenesis into the fly's gut, on the fly infection by the trypanosome. Nevertheless, the results are encouraging insofar as the technical approach works on the couple G. p. gambiensis/T. brucei gambiense. The next step will be to optimize the system and test other targets chosen among the ESPs (Excreted-Secreted Proteins) of the trypanosome secretum, or the differentially expressed genes associated with the sensitivity/resistance of the fly to trypanosome infection
Clé d'identification des principales Poaceae adventices de La Réunion - sur la base des caractères végétatifs - version juin 2025
Get PDFExtraction and quantification of carotenoid contents in cassava roots, leaves, flour, and derived food products
No full textCarotenoids in cassava, such as β-carotene, play a vital role in human health as health-promoting com-pounds and precursors to vitamin A. Understanding the carotenoid content in cassava-based foods is essential for assessing their nutritional value and potential health benefits. This study explores the extraction and quantification of carotenoids in cassava roots, leaves, flour, and products derived from cassava flour. Various analytical techniques, including high-performance liquid chromatography, spectrophotometry, and near-infrared spectroscopy (NIRS), are utilized to measure carotenoid content accurately. Optimization of extraction methods is crucial for efficient carotenoid recovery and quantification. Notably, the study reveals a non-uniform distribution of carotenoid concentrations within different sections of cassava roots, empha-sizing the need for precise sampling strategies. NIRS emerges as a rapid and reliable predictive tool, complementing traditional methods by enabling high-throughput screening of carotenoid levels. Optimiz-ing extraction methods and leveraging these analytical tools contribute to better understanding the nutritional profile of cassava-based foods and their potential health benefits
Bottom and top internodes subjected to interactions with genotype in Miscanthus: impact of biochemical composition and anatomy on stem-based composites mechanical properties
Get PDFMiscanthus (Miscanthus Andersson) is a perennial grass for which biomaterials market has taken growing interest. Our objective was to evaluate the effect of stem internode position in Miscanthus × giganteus and Miscanthus sinensis and the impact of its anatomy and biochemical composition on internode-based composites' mechanical properties. Stems' bottom and top internodes were sampled for two genotypes of each species in two different years and separately added to a polypropylene matrix, and the mechanical properties of the internode-reinforced composites were measured. Before composite production, the internodes were extensively phenotyped for biochemical composition and anatomy. Stems' bottom and top internode-based composites yielded different modulus (3203 and 2988 MPa, respectively), while tensile strength was similar (36.4 and 36.5 MPa, respectively). Significant genotype × internode interactions occurred for most variables, mainly due to differences among species, since both Miscanthus sinensis clones proved to be more stable than both Miscanthus × giganteus clones for modulus (4% and 10.2%, respectively). Regarding tensile strength, the species showed small but opposite differences between internodes. Tensile strength and modulus were rather close only in the top internodes, where good mechanical properties were associated with the lowest values of vascular bundles number and section area and highest parenchyma tissue, while opposite results were obtained in the bottom ones, only for tensile strength. Miscanthus sinensis species proved to be interesting for the stability improvement of composite mechanical properties. It appears essential for experimental purposes to stratify the sampling by internode in order to be representative of the whole stem
Tropical timber: a shrinking market
No full textThe year 2024 saw changes in the relative prices of tropical timber and was marked by a contraction in exports linked to the slowdown in Chinese demand. Indonesian plywood prices fell back slightly throughout the year, but sawnwood prices rose overall. A new trend is emerging for African logs: their prices are falling, while sawnwood prices are tending to rise. This contrasts with the situation in recent years, when prices for African logs were relatively high due to their reduced availability on international markets. However, restrictions on the export of logs by a growing number of countries have led many wood-processing plants in Europe to cease operations or to convert. As a result, demand for logs is falling, while demand for sawn timber and veneer is rising, and prices are adjusting. However, this trend will need to be confirmed in the coming years, as China's demand for tropical logs, although declining over the past decade (5.7 million m3 imported in 2023 compared with 13.2 million in 2014), remains high in the face of rapidly shrinking supply. And Indian demand for logs is set to increase
Rôle du statut redox-pH dans les interactions sol-plante-insectes ravageurs pour une protection agroécologique du riz Oryza sativa (Poaceae) à Madagascar
No full textL'hypothèse électrochimique, explicative des répartitions spécifiques des foreurs de tiges et des vers blancs (VB), ravageurs majeurs du riz à Madagascar, a été testée en région Fitovinany et Vakinankaratra. Cette hypothèse, basée sur le statut pH-redox du sol et des plantes, associe d'une part l'hémibiotrophe s.l. M. separatella et les VB saprophages à des milieux alcalins et réduits, et d'autre part le nécrotrophe s.l. S. calamistis et les VB rhizophages à des milieux acides et oxydés. En région Fitovinany, la présence exclusive de M. separatella sur sols hydromorphes a été dans le sens de cette hypothèse. En région Vakinankaratra, l'hypothèse a été confirmée par les mesures électrochimiques des feuilles de riz par spectrométrie proche infrarouge le long d'une toposéquence, couplée à la caractérisation de la flore adventice et à celle de l'entomofaune telllurique. Ainsi, le riz a été plus oxydé à mi-pente qu'en bas de pente et les adventices bioindicatrices de sols réduits ont été trouvées en bas de pente. Les larves d'Hyposerica sp. et Triodontus nitidulus, VB considérés comme rhizophages facultatifs, ont été trouvées en haut de pente et à mi-pente, et à mi-pente et en bas de pente. Les résultats d'une étude de laboratoire en mésocosme ont suggéré une plasticité trophique des larves d'Hyposerica sp., moins agressives en sol complémenté en paille de riz. Les résultats obtenus plaident en faveur d'une gestion agroécologique des VB en riz pluvial, en créant des conditions réductrices par l'incorporation de biomasse végétale fraîche au sol, contrairement au labour qui oxyde le sol
Breeding of new coffee varieties as a key strategy to improve coffee sustainability in response to the climate change
No full textDespite the differences between the two cultivated species Coffea arabica and C. canephora, in terms of breeding system and genetic diversity, there are some key elements in common for creating C. arabica and C. canephora varieties adapted to global warming (GW). The main existing farming systems are common to both species, and impose, for each farming system, specifications to the breeders that are quite similar for these species. To speed-up the selection of C. canephora, we propose a crossbreeding program using the widest possible genetic diversity including very closely related species (C. congensis and C. brevipes), followed by clonal selection and assisted by multi-trait and multi-environment genomic-phenomic selection. Since C. arabica contains an entire sub-genome of C. canephora, this makes the latter, the cornerstone of C. arabica breeding. For this species with very low polymorphism, the use of specific hybridisation for the introgression of resistance and adaptation genes is an absolute necessity. Introgressed materials can then be crossed with wild Ethiopian male-sterile genotypes to create high-yielding F1 hybrid. However, given the length of selection cycles, the use of genome-editing techniques enabling the transfer of large and precise quantities of DNA seems essential for introgressing several traits at once. Most of the main target traits seeking sustainability and resilience for the main farming systems are currently considered, but some constitute “blind spots”. However, for both producing species, breeding based on performance, high yield and yield stability in environments representing targeted stress scenarios, remains the proven method for selecting GW-adapted coffee varieties in the next decade