Influence du changement climatique sur la diversité inter et intra-spécifique des plantes cultivées à Tougou au nord du Burkina Faso

L’objectif de l’étude est d’évaluer la diversité taxonomique et la variabilité inter et intra-spécifique des plantes cultivées non spontanées dans un contexte de changement climatique. Les données sont collectées à l’aide d’une enquête au près de 75 producteurs menée suivant des interviews semi-structurées. Les résultats ont révélé l’existence de 122 écotypes appartenant à 49 espèces, 39 genres et 22 familles. La diversité interspécifique représentait 73% de la diversité des plantes cultivées au plan national. La variabilité intraspécifique était faible comparée à la variabilité au plan national. Elle était plus élevée chez les céréales et les cultures potagères pluviales avec 2 à 10 écotypes par espèce contre 1 à 3 écotypes par espèce chez les cultures maraîchères. Les écotypes ayant un cycle de plus de 90 jours représentant 10,5% de l’ensemble des écotypes recensés, sont menacés de disparition à cause du changement climatique. Une stratégie de collecte, de conservation, d’amélioration et de promotion de ces ressources ainsi que la restauration des écosystèmes dégradés s’avèrent nécessaire pour le maintien de la phytodiversité cultivée.Mots clés: Burkina Faso, agro biodiversité, écotype, espèces menacées, conservatio

Effet de l’inoculum «Compost Plus» Sur le Compostage des Tiges de Cotonnier et les Rendements en Coton au Burkina Faso

Afin de recycler les tiges de cotonnier en compost, l’inoculum «compost plus» comparé au fumier habituellement utilisé comme ferment, a été testé par un groupe de paysans en 2006. La durée de compostage, les consommations d’eau et les caractéristiques chimiques des composts ont été déterminées. Les composts obtenus ont été associés à la fumure minérale vulgarisée, à 5 t ha-1 pour déterminer leur efficacité sur les rendements du cotonnier. La durée moyenne du compostage des tiges de cotonnier a été de 70 et 64 j avec « compost plus » et le fumier, respectivement. Durant le compostage, en saison sèche, les consommations d’eau par tonne de tiges de cotonnier avec «compost plus» (3584 l) ont été plus importantes que celles avec le fumier (2077 l). Ces quantités d’eau ont diminué significativement, en saison pluvieuse, de même que la durée de maturation du compost. Les composts obtenus se sont révélés pauvres en P et riches en N et en K. Ces composts, associés à la fumure minérale vulgarisée, ont amélioré significativement les rendements en coton graine. L’utilisation de « compost plus » pourrait améliorer les rendements à travers un recyclage approprié des tiges de cotonnier.Mots clés : Tiges de cotonnier, compostage, « compost plus », fumier, rendement.The inoculum «compost plus», as compared to manure, usually used as ferment, was used for the composting of cotton straws by farmers in 2006. Composting time, quantities of water used and chemical properties of the compost were determined. The use of the compost, at the rate of 5 t ha-1, associated with conventional mineral fertilizer, was evaluated for cotton seed yield. The results showed that the time for cotton straw composting with «compost plus» and manure was 70 and 64 days, respectively. The quantity of water used, with «compost plus» during the dry season was higher (3584 l t-1) than that of the manure (2077 l t-1). The quantities of water decreased significantly during the rainy season. The same was true for composting time. The composts obtained with «compost plus» and manure, were lower in P and higher in N and K. Seed cotton yield increased significantly with the use of compost associated to mineral fertilizer. Finally the use of the «compost plus» inoculum could be an alternative for the recycling of cotton straws, with an increase in the organic matter content of soil and cotton production.Key words : Cotton straws, composting, «compost plus», manure, yield

Management of Parkia biglobosa in the field of farmers in selected sites in Burkina Faso

Parkia biglobosa is ranked as one of the most important agroforestry multipurpose tree species in Sahelo-Sudanian zone. The National Tree Seed Center (CNSF) of Burkina Faso has been involved in a breeding programme of this species for many years and has already conducted several research activities (eg. germplasm collection, provenance trials establishment, selection of the best promising trees for propagation). To better conserve and guide the breeding program, it is important to understand how farmers perceive and manage the species in their fields. A survey was conducted in two villages in southern Burkina Faso to describe the farmers' practices with regard to encouraging regeneration of tree species in their fields, with a special emphasis on Parkia biglobosa. The survey targeted 150 people categorised by gender, ethnic group and status of residence. The results show that Parkia biglobosa is the most appreciated indigenous species across ethnic and gender groups. Its maintenance in the landscape is favoured by both the protection of spontaneous regeneration by farmers when they clear the land for agriculture, and by active planting. The species is valued both for its commercial use and human consumption in the household. The survey indicated a significant difference in the practices undertaken by women and men to safeguard regeneration. With regard to the preferred traits of Parkia biglobosa individuals, also some differences between genders emerge. The level of appreciation shown by farmers for Parkia biglobosa and the indications about what traits are most preferred are useful guidance in the identification of optimal sources of reproductive material to be made available to farmers through different channels. The results also indicated the need to couple the analyses of farmers' perception of trait variation among individuals with a systematic morphological characterisation of the various morphological types identified

Acidification des sols ferrugineux et ferrallitiques dans les systèmes de production cotonnière au Burkina Faso

La productivité des systèmes de culture coton-céréales est menacée par la dégradation et l’acidification des terres. Afin de déterminer les causes de l’acidification des sols dans la zone cotonnière du Burkina Faso, une expérimentation a été conduite pendant deux années, en milieu paysan, sur des sols ferrugineux et ferrallitiques, respectivement sur les sites de Dohoun et Balla. Trois modes d’exploitation des terres, définis par la jachère, la culture attelée et la culture motorisée, ont été comparés pour déterminer leurs effets sur les caractéristiques physico-chimiques des sols étudiés. Par rapport à la jachère, comparée à la culture attelée, la culture motorisée a entraîné, en surface (0-20 cm) des sols ferrugineux et ferrallitiques, une augmentation des teneurs en sable de 8 à 12% et une baisse du taux d’argile de 35% qui expose ces sols à l’acidification. Contrairement à la jachère, la culture motorisée a entraîné des pertes significatives de carbone et d’azote, qui rendent les sols plus sensibles à l’acidification qu’en culture attelée. L’exploitation des terres s’est aussi traduite par une baisse significative des teneurs des cations majeurs du complexe adsorbant (Ca2+ et Mg2+), de la somme des bases échangeables (SBE) et de la capacité d’échange cationique (CEC), accentuant la vulnérabilité à l’acidification sous culture motorisée. La dégradation des sols cultivés a été plus importante pour les sols ferrallitiques qu’au niveau des sols ferrugineux, dont la CEC a été 2 à 3 fois plus élevée. La culture attelée et la culture motorisée, pratiquées, le plus souvent, sans restitution organique, se sont révélées comme étant des causes de l’acidification des sols ferrallitiques, plus accentuée que celle des sols ferrugineux. L’étude recommande d’adopter des techniques adéquates de travail du sol et de procéder à des amendements appropriés pour atténuer l’acidification et garantir la durabilité des systèmes de production.Mots clés: Exploitation des terres, acidification, sol ferrugineux, sol ferrallitique, zone cotonnière

Genetic diversity of Parkia biglobosa (African locust bean) and its implications for conservation strategies

Parkia biglobosa is an African Savannah tree with a wide range from Senegal to Uganda between the latitudes 5 and 15° in the North of equator. It is well-known as an agroforestry tree but also as a medicinal and food tree. Seeds, barks, roots, leaves and flowers are used to treat more than 80 diseases and complaints while fermented seeds and pulp of fruits have highly nutritional and commercial values. Understanding the level and distribution of genetic diversity of a widespread species such P. biglobosa is crucial for its conservation and sustainable utilisation. The genetic diversity and population structure were investigated using height nuclear microsatellites developed for the species. The sampling included 84 populations from twelve countries in West and Central Africa. The height microsatellite loci were highly polymorphic and did not show evidence of null alleles. A total of 217 alleles were revealed among the 1,610 genotypes of P. biglobosa. The number of alleles per locus was ranged from 17 to 50 with an average of 27 alleles per locus. The estimates of genetic diversity were moderate for the populations of extreme West Africa and Central Africa and were high to populations in the centre of West Africa. Individual-based assignment using admixture model with correlated allele frequencies revealed strong genetically structured populations across P. biglobosa range in West and Central Africa. The clustering analysis showed five most plausible subpopulations for the biogeographic study in West and Central Africa. Analysis of molecular variance partitioned the molecular variation 9.10% among groups, 2.71% among populations within groups and 88.19% within populations. Overall, the genetic differentiation among populations was moderate (FST=0.118; P<0.001). In regard to the distribution of intraspecific diversity, we also discussed the implications for conservation and sustainable use of the species

Efficacy of the association of cover crops with maize and direct sowing short-term effect on crops? yields in maize-cotton cropping system in Western Burkina Faso.

To improve the productivity and sustainability of cotton and cereals based system, direct sow ing under mulch was tested for its efficacy on cotton and maize yields on the research station of Farako - Bâ, in Western Burkina Faso. The experimental design was a complete randomized blocks of Fisher with four replications. Conventional tillage by annual moldboard plowing (T7) was compared with direct sowing under mulch -based cropping system (DMC) using maize association with cover crop s defined as: maize without cover crop (T1), maize +Brachiaria ruziziensis(T2), maize + B. ruziziensis+ Mucuna cochinchinensis (T3), maize + B. ruziziensis+ Panicum maximum (T4), maize + B. ruziziensis + Stylosantes hamata (T5), and maize + Crotalaria juncea (T6). Cover crops were planted 21 days after maize emergence between the rows of this main crop. The biomass produced by the cover crops and maize straws were evaluated as well as maize and cotton yields, during the first 6 years of the study, from 2010 to 2015. Results showed that among cover crops, the biomass production was significantly lower with C. juncea. The associations of cover crops with maize increased significantly the production of total dry matter compared to plots without cover crops, in the conventional tillage. Association with cover crops did not influence significantly nitrogen, phosphorus and potassium contents of maize and the maize’s yields even if the depressive effects were recorded. Compared to the conventional tillage, the DMC appeared also effective on seed cotton yields even without a significant improvement during the 6 first years of the study . These promising results, confirm the feasibility in tropical conditions of DMC which must be continued to better analyze its long-term effects on soil properties

Interleukin-10 and soluble tumor necrosis factor receptor II are potential biomarkers of Plasmodium falciparum infections in pregnant women: a case-control study from Nanoro, Burkina Faso

Background: Diagnosis of malaria in pregnancy is problematic due to the low sensitivity of conventional diagnostic tests (rapid diagnostic test and microscopy), which is exacerbated due to low peripheral parasite densities, and lack of clinical symptoms. In this study, six potential biomarkers to support malaria diagnosis in pregnancy were evaluated.Methods: Blood samples were collected from pregnant women at antenatal clinic visits and at delivery. Microscopy and real-time PCR were performed for malaria diagnosis and biomarker analyses were performed by ELISA (interleukin 10, IL-10; tumor necrosis factor-α, TNF-α; soluble tumor necrosis factor receptor II, sTNF-RII; soluble fms-like tyrosine kinase 1, sFlt-1; leptin and apolipoprotein B, Apo-B). A placental biopsy was collected at delivery to determine placental malaria.Results: IL-10 and sTNF-RII were significantly higher at all time-points in malaria-infected women (p < 0.001). Both markers were also positively associated with parasite density (p < 0.001 and p = 0.003 for IL-10 and sTNF-RII respectively). IL-10 levels at delivery, but not during pregnancy, were negatively associated with birth weight. A prediction model was created using IL-10 and sTNF-RII cut-off points. For primigravidae the model had a sensitivity of 88.9% (95%CI 45.7–98.7%) and specificity of 83.3% (95% CI 57.1–94.9%) for diagnosing malaria during pregnancy. For secundi- and multigravidae the sensitivity (81.8% and 56.5% respectively) was lower, while specificity (100.0% and 94.3% respectively) was relatively high. Sub-microscopic infections were detected in 2 out of 3 secundi- and 5 out of 12 multigravidae.Conclusions: The combination of biomarkers IL-10 and sTNF-RII have the potential to support malaria diagnosis in pregnancy. Additional markers may be needed to increase sensitivity and specificity, this is of particular importance in populations with sub-microscopic infections or in whom other inflammatory diseases are prevalent

Increase in the prevalence of mutations associated with sulfadoxine-pyrimethamine resistance in Plasmodium falciparum isolates collected from early to late pregnancy in Nanoro, Burkina Faso.

BACKGROUND: Pregnant women are a high-risk group for Plasmodium falciparum infections, which may result in maternal anaemia and low birth weight newborns, among other adverse birth outcomes. Intermittent preventive treatment with sulfadoxine-pyrimethamine during pregnancy (IPTp-SP) is widely implemented to prevent these negative effects of malaria. However, resistance against SP by P. falciparum may decrease efficacy of IPTp-SP. Combinations of point mutations in the dhps (codons A437, K540) and dhfr genes (codons N51, C59, S108) of P. falciparum are associated with SP resistance. In this study the prevalence of SP resistance mutations was determined among P. falciparum found in pregnant women and the general population (GP) from Nanoro, Burkina Faso and the association of IPTp-SP dosing and other variables with mutations was studied. METHODS: Blood spots on filter papers were collected from pregnant women at their first antenatal care visit (ANC booking) and at delivery, from an ongoing trial and from the GP in a cross-sectional survey. The dhps and dhfr genes were amplified by nested PCR and products were sequenced to identify mutations conferring resistance (ANC booking, n = 400; delivery, n = 223; GP, n = 400). Prevalence was estimated with generalized estimating equations and for multivariate analyses mixed effects logistic regression was used. RESULTS: The prevalence of the triple dhfr mutation was high, and significantly higher in the GP and at delivery than at ANC booking, but it did not affect birth weight. Furthermore, quintuple mutations (triple dhfr and double dhps mutations) were found for the first time in Burkina Faso. IPTp-SP did not significantly affect the occurrence of any of the mutations, but high transmission season was associated with increased mutation prevalence in delivery samples. It is unclear why the prevalence of mutations was higher in the GP than in pregnant women at ANC booking. CONCLUSION: The high number of mutants and the presence of quintuple mutants in Burkina Faso confirm concerns about the efficacy of IPTp-SP in the near future. Other drug combinations to tackle malaria in pregnancy should, therefore, be explored. An increase in mutation prevalence due to IPTp-SP dosing could not be confirmed

Genetic conservation in Parkia biglobosa (Fabaceae: Mimosoideae) - what do we know?

The medicinal and food tree species Parkia biglobosa (Faba­ceae: Mimosoideae) is widespread in the Sudanian savannahs of sub-Saharan Africa, where it has a strong socio-cultural and economic importance. Populations of this species are highly threatened in large parts of its range due to over exploitation and environmental degradation. In the light of climatic changes, safeguarding the genetic diversity of the species is crucial to foster adaptation and to support its long-term survival. Genetic insight is also relevant to guide sustainable harvesting. This paper has the objective to review information on the species’ geographic distribution, reproductive biology, genetic characteristics and existing conservation practices, and to identify knowledge gaps to orientate future conservation and research focus. The literature review revealed that the species is mainly out-crossed and is pollinated by a diversity of vectors, including bats that allow long-pollen dispersal. When bats are absent, pollination is mainly carried out by honey bees and stingless bees and in such case pollen-mediated gene flow is relatively restricted. Data of a large-scale genetic study based on allozyme markers showing a moderate genetic differentiation among populations were reanalyzed using an inverse dis­tance weighted interpolation function. Three distinctive regions of diversity based on allelic richness and expected heterozygosity were identified. Finally, we discuss future chal­lenges for genetic conservation by emphasizing the need to use both neutral and adaptive markers in future research

Auswirkungen von Biokohle, Abwasserbewässerung und Düngung auf Bodeneigenschaften unter urbaner Landwirtschaft in Westafrika

Die zunehmende nachfrageorientierte Intensivierung der Agrarproduktion im semiariden Westafrika wird aus bodenkundlicher Sicht durch geringe Bodenfruchtbarkeit und hohen Bodendegradationsraten limitiert. Als vielversprechende Möglichkeit zur Bodenverbesserung wird seit einiger Zeit Biokohle vorgeschlagen. Zudem wird im städtischen Umfeld ungeklärtes Abwasser zur Bewässerung eingesetzt. Denn Abwasser wird nicht nur als ganzjährige Wasserquelle, sondern auch als Nährstoffquelle für Böden und Pflanzen betrachtet, trotz des hohen Kontaminationsrisikos durch Pathogene und Schwermetalle. Wissenslücken bestehen vor allem bezüglich der Wechselwirkungen zwischen Biokohle, Düngung und Abwasserbewässerung und Bodeneigenschaften. Das Ziel dieser Studie war daher die Untersuchung der Auswirkungen von Biokohle (hergestellt aus Ernterückständen des Mais- und Reisanbaus), organischer und anorganischer Düngung, Bewässerungsqualität und Bewässerungsquantität auf die Bodeneigenschaften von zwei sandigen, humus- und nährstoffarmen Böden unter Gemüseanbau im urbanen Raum von Tamale (Nordghana) und Ouagadougou (Burkina Faso) über einen Zeitraum von zwei Jahren. Die Applikation von Biokohle bewirkte eine Verdoppelung der C-Vorräte auf beiden Standorten, allerdings wurden anschließend C-Verluste in Höhe von 35 % in Ouagadougou und 46 % in Tamale beobachtet. Korrigiert durch die Auswirkungen der Landnutzungsänderungen verringern sich die C-Verluste in Tamale auf ebenfalls 35 %. Beide Biokohlen hatten keine Auswirkungen auf den pH-Wert, die KAK und das verfügbare P. Die Applikation von Reishülsenbiokohle führte zur N-Retention (18 % höhere N-Vorräte im Vergleich zur Kontrolle), wohingegen die Maisspindelkohle keine Auswirkung auf den N-Haushalt hatte. In Tamale führte die NPK Düngung zur Erhöhung des verfügbaren P sowie zur Versauerung (0.65 pH-Einheiten) und zur Verringerung der effektiven Basensättigung (von nahezu 100% auf 93%) aufgrund der geringen Pufferkapazität des Bodens. In Ouagadougou führte die regelmäßige organische Düngung mit Rindermist zur Erhöhung der C- und N-Vorräte und der KAK. Die einzigen Auswirkungen der Abwasserbewässerung waren ein Anstieg des austauschbaren Natriums und des pH Wertes. Die Ergebnisse der Untersuchungen an beiden Standorten zeigen, dass die Auswirkungen von Biokohle, die aus Ernterückständen hergestellt wurde, und Abwasserbewässerung auf die Bodeneigenschaften geringer sind als in früheren Studien beschrieben wurde