The effect of green manure of gliricidia (Gliricidia sepium (Jacq.) Walp) leguminous plants applied for cereal maize cultivation and N uptake by cereal were investigated and analyzed in relation to influence of dual inoculation of gliricidia with microbial symbionts. Two pot experiments were conducted in greenhouse. The first trial was set up to enhance growth of gliricidia with exotic and indigenous rhizobial strains and arbuscular mycorrhizal fungus and the second to determine the effect of gliricidia organic material on maize growth. Direct 15N-labelling techniques were used to estimate N-fixed by gliricidia plant and N uptake of maize cereal crop from green manuring was calculated. Growth of gliricidia trees estimated by aboveground biomass production and N fixed were positively affected by dual inoculations. This study showed that shoot dry weight and N accumulation of maize cultivated under gliricidia green manure were influenced by its application and indirectly by microbial treatments. The N recovery by the maize accounted 17.32% to 26.52% of N applied as gliricidia organic material. Gliricidia green manure N accumulation and release, and afterward microbial inoculations were substantially determining on maize crop N uptake and growth in sandy soil of Sub-Saharian Africa.
Cowpea, Vigna unguiculata (L.) Walp. presents phenotypical variabilities and in order to study the genetic diversity of cultivated Senegalese varieties, two experimental approaches were used. First, a physiological characterization based on nitrogen fixation was used to assess cowpea breeding lines. Inoculation with two Bradyrhizobium strains (NGR234 and ISRA312), showed a difference in nitrogen fixation potential between the cowpea varieties. Diongoma is the highest nitrogen fixing variety, whereas Mouride is the lowest. The second approach employed genetic characterization based on DNA polymorphism to screen. Results suggest that random amplified polymorphic DNA (RAPD) technology can be used to reorganize the national germplasm in order to eliminate the putative duplicates, and to identify elite varieties.
Sesame (Sesamum indicum L.), an annual self-pollinating plant native to Africa and India, is very sensitive to the stages of germination and sowing but moderately tolerant to water and salt stress. The objective of this
Parmi les microorganismes de la rhizosphère, figurent les Pseudomonas spp fluorescents qui sont des bactéries d'intérêt agricole (Plant Growth Promoting Rhizobacteria). Ces Pseudomonas pourraient permettre le développement de certaines plantes des sols salés et jouer ainsi un rôle important dans la réhabilitation de ces sols au Sénégal. Ainsi l'objectif de cette étude est d'évaluer l'effet de différentes concentrations de NaCl sur la croissance de Pseudomonas spp fluorescents. Des prélèvements de sol ont été effectués au niveau de la rhizosphère de trois spéculations (oignon, aubergine, tomate) et sur sol nu. Les souches ont été isolées par la méthode des suspensions dilutions, puis ensemencées sur milieu King B. L'identification des isolats a été effectuée par observation sur table UV. Trois isolats ont été sélectionnés et purifiés sur milieu King B pour chaque échantillon de sol. Afin d'évaluer l'effet de la salinité sur ces souches, les concentrations suivantes ont été appliquées : 0 M ; 0,17 M ; 0,34 M ; 0,51 M ; 0,70 M ; 0,85 M et 1,03 M. Les résultats obtenus après 72 h d'incubation montrent que les souches se développent pour des concentrations en NaCl allant de 0 M à 0,51 M. Les concentrations supérieures entraînent une réduction du nombre de colonies pour tous les isolats. Il existe un seuil de tolérance au sel pour chaque souche de Pseudomonas. Cependant, les souches isolées de la rhizosphère de plants d'oignon sont plus résistantes au sel par rapport aux isolats des rhizosphères de plants de tomate et d'aubergine. Ces isolats de Pseudomonas pourraient être utilisés dans les sols salés afin d'améliorer les rendements des cultures.
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