L'acacia au Sénégal

La variabilité intra et interspécifique de la fixation biologique de l'azote a été étudiée chez les acacias. Cette variabilité se manifeste d'abord dans l'aptitude des espèces d'#Acacia à former des nodules avec des souches de #Rhizobium ou de #Bradyrhizobium. Ensuite, il a été mis en évidence une différence dans le potentiel fixateur d'azote entre les espèces d'#Acacia : #A. mangium, #A. seyal et #A. raddiana ont un potentiel élevé alors qu'#A. senegal, #A. pellita et #Faidherbia albida ont un potentiel faible. La variabilité intraspécifique des acacias à fixer l'azote a également été observée dans le cas de #F. albida : la provenance de Kabrousse a le potentiel fixateur le plus élevé ; les provenances de Merina et Dangalma ne fixent pas d'azote. Cette diversité traduit probablement l'existence d'une variabilité génétique chez #Acacia. (Résumé d'auteur

Sesbania rostrata as green manure for lowland rice in Casamance (Senegal)

The stem-nodulating tropical legume, #Sesbania rostrata, was grown for seven consecutive years for 35-42 days in the pre-rice niche of traditional Casamance (south Senegal) rainfed lowland fields under the management of both researchers and farmers. The incorporation of about 25-35 Mg/ha of fresh green manure (GM) biomass resulted in an average N accumulation of 90-150 kg N/ha. Lowland rice-grain yields increased from 2 Mg/ha in weedy fallow control plots to about 4 Mg/ha where seed-inoculated #S. rostrata was incorporated. #Sesbania rostrata$ GM technology may contribute to increase rice production in casamance and warrants to be extended to regions with similar conditions. (Résumé d'auteur

Evaluation de l'impact bioclinique et social, individuel et collectif, du traitement ARV chez des patients VIH-1 pris en charge depuis 10 ans dans le cadre de l'ISAARV : cohorte ANRS 1215 : rapport final

This report presents the results from studies conducted between 2009 and 2011 in Senegal in the framework of the ANRS 1215 research program aimed at documenting the long-term impact of therapeutic treatment with antiretroviral drugs. The 400 participants from ANRS cohort 1215 began treatment between 1998 and 2002; they were among the first people living with HIV in Africa to receive ARV therapies. These studies were conducted using a multidisciplinary approach. The main themes are: - Medical science: immune restoration among patients who were the most immunocompromised, virologic failure and resistance mutations, changes in treatment efficacy and mortality, a description of comorbidities, an investigation of the effects of aging, and sexual health. - Public health and epidemiology: changes in treatment adherence, socioeconomic outcomes for patients, sociomedical conditions and determinants for treatment failure, and mental health. - Social sciences: patient's experience of the disease and treatment over the long term, social aspects of childbearing for HIV-positive women on ARVs, perceptions and practices related to prevention of sexual transmission of HIV for patients on ARVs, perceptions of lipodystrophy, vulnerability among widows and the aged, critical analysis of the degree of stigmatization, cost analysis of treatment and drugs, and systems for ethical research. Each of these themes led to specific, often overlapping, studies that used a complementary approach. This report is organized into five sections, with a standardized format for writing conventions, presentation, and bylines, according to the uses in the dominant disciplinary field for each part.Ce rapport rassemble les résultats des études réalisées entre 2009 et 2011 au Sénégal dans le cadre du programme de recherche ANRS 1215 qui avait pour objectif de documenter l'impact à long terme de la prise en charge thérapeutique par les médicaments antirétroviraux. Les 400 participants de la cohorte ANRS 1215 ont débuté leur traitement entre 1998 et 2002, ils font partie des premières personnes vivant avec le VIH en Afrique à avoir reçu des traitements ARV. Ces études ont été menées dans une perspective pluridisciplinaire. Les principales thématiques sont : - en sciences médicales : la restauration immunologique chez les patients les plus immunodéprimés, les échecs virologiques et les mutations de résistances, l'évolution de l'efficacité thérapeutique et de la mortalité, la description des co-morbidités, l'étude des effets du vieillissement, et la santé sexuelle. - en santé publique et épidémiologie : l'évolution de l'observance thérapeutique, le devenir socio-économique des patients, les conditions et déterminants socio-médicaux des échecs thérapeutiques, la santé mentale. - en sciences sociales : l'expérience de la maladie et du traitement à long terme, les aspects sociaux de la procréation chez les femmes vivant avec le VIH traitées par ARV, les perceptions et pratiques relatives à la prévention de la transmission sexuelle du VIH chez les patients traités par ARV, la perception des lipodystrophies, la vulnérabilité des veuves et des personnes âgées, l'analyse critique de la mesure de la stigmatisation, l'étude des coûts de prise en charge et des médicaments, les dispositifs éthiques de la recherche. Chacun de ces thèmes a conduit à des investigations spécifiques, le plus souvent associées, dans des approches visant la complémentarité. Ce rapport est organisé en cinq parties, ayant une cohérence interne au plan des conventions de rédaction, de présentation et de signatures, suivant les usages des champs disciplinaires dominants dans chaque partie

Biological nitrogen fixation in Crotalaria species estimated using the 15N isotope dilution method

A greenhouse experiment was conducted to measure nitrogen fixation in three Crotalaria species : C. ochroleuca, C. perrottetii and C. retusa growing in Senegal by using 15N direct isotope dilution technique. Two non-fixing plants, Senna obtusifolia and Senna occidentalis served as reference plants. The amount of nitrogen fixed two months after planting was obtained using the average of the two reference plants. The atom % 15N excess in the Crotalaria species was significantly lower than that of the reference plants, indicating that significant nitrogen fixation occurred in the three plants. Significant differences were observed between the Crotalaria species; C. ochroleuca yielded more dry matter weight and total nitrogen than did C. perrottetti and C. retusa. The % nitrogen derived from atmosphere (%Ndfa) in leaves and stems was also higher in C. ochroleuca. There was no significant difference in %Ndfa in the whole plant between the three Crotalaria species (47% to 53%). In contrast, interspecific variability was observed based on the %Ndfa. C. ochroleuca significantly exhibited the higher amount of total nitrogen fixed, equivalent to 83 kg of nitrogen fixed per hectare. Based on these data, it was concluded that C. ochroleuca could be used in multiple cropping systems in Senegal for making more nitrogen available to other plants. (African Journal of Biotechnology: 2002 1(1): 17-22

Dérivation du haut appareil urinaire par une sonde JJ: indications et résultatsdansuneétude rétrospective et monocentrique

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Water-condition effects on rhizobia competition for cowpea nodule occupancy

Two indigenous bradyrhizobia strains displaying different natural behaviours towards water regime (strain ORS 3257, nodulating more frequently in favourable-water conditions and strain ORS 3260, in limited-water conditions) were studied for their competitivity for nodulation of cowpea (Mouridecultivar) under favourable and limited water conditions in non-sterile soil. The nodule occupancy was studied by PCR-RFLP analysis. Both strains showed good competition with other indigenous rhizobia populations under favourable- and limited-water conditions. Competition between the inoculatedstrains in the mixture varied between water regimes. In non-limited-water conditions, strain ORS 3257 was the best competitor, whereas in limited-water conditions, strain ORS 3260 was the best competitor. Results indicated that screening of strains according to their environmental origin could ensuresuccessful rhizobia inoculatio

Effect of arbuscular mycorrhizal fungal inoculation on growth, and nutrient uptake of the two grass species, Leptochloa fusca (L.) Stapf and Sporobolus robustus Kunth, under greenhouse conditions

The aim of our work was to assess the effect of inoculation with three arbuscular mycorrhizal fungi (AMF) (Rhizoglomus aggregatum (N.C. Schenck and G.S. Sm.) Sieverd., G.A. Silva and Oeh., Funneliformis mosseae (T.H. Nicolson and Gerd.) C. Walker and A. Schüssler. and Rhizoglomus intraradices (N.C. Schenck and G.S. Sm.) Sieverd., G.A. Silva and Oehl.), and a mixed inoculum of these AMF on root colonization, biomass production, mycorrhizal dependency (MD) and shoot mineral contents of two salt tolerant grasses Leptochloa fusca L. Stapf and Sporobolus robusts Kunth. After four months of growth in a sterilized soil and greenhouse conditions, grasses inoculated with AMF showed significantly higher total biomass production than non-inoculated seedlings. MD and shoot mineral contents (especially P) varied with AMF host plants. Maximum values of MD (13%) were observed in L. fusca and S. robustus seedlings when inoculated with R. intraradices and F. mosseae, respectively. Only P contents were higher in the S. robustus/mixed-AMF combinations than the other treatments. These results demonstrate the potential benefits in our experimental conditions of AM inoculation for improving growth and P acquisition particularly in the L. fusca/ F. mosseae and S. robustus/mixed-AMF combinations.Key words: Grass species, symbiosis, mycorrhizal dependency, mineral nutrition