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

Réponse à la double inoculation mycorhizienne et rhizobienne du niébé (variété, KVX396-4-5-2D) cultivé au Burkina Faso

Le niébé vit en symbiose avec des champignons mycorhiziens arbusculaires (CMA) et rhizobiums du sol susceptibles d’améliorer sa nutrition hydrominérale et sa croissance. Cette étude avait pour objectif d’évaluer la réponse du niébé (variété KVX 396-4-5-2D) à l’inoculation rhizobienne et/ou mycorhizienne. KVX 396-4-5-2D (KVX) a été inoculée en serre avec cinq inoculums de CMA [Glomus aggregatum (Ga), Glomus mossae (Gm), Rhizophagus irregularis (Ri), Glomus fasciculatum (Gf), Glomus verrucullosum (Gv)] et une souche de rhizobium (ORS 3409). Après 45 jours de culture, les plants ont été récoltés et les paramètres de croissance (hauteur et biomasses), de mycorhization et de nodulation ont été mesurés. Les résultats montrent que l’inoculation améliore la croissance en hauteur et la biomasse totale des plants de KVX. La souche Ga améliore de 70% la production de biomasse totale de KVX. Aussi, la double inoculation ORS3409+Ga est plus bénéfique aux plants de la variété de niébé utilisée avec une amélioration de la croissance en hauteur de 8,82%. De ces résultats, il ressort que l’inoculum Ga améliore significativement la croissance de la variété de niébé KVX au stade floraison-fructification.Mots clés : Champignons mycorhiziens arbusculaires, rhizobium, inoculation, niébé

Effets des systèmes de culture et de la variété de niébé (Vigna unguiculata L. Walp) sur la diversité de bradyrhizobia symbiotique et et le rendements de mil dans la zone soudano-sahélienne du Mali

International audienceCowpea is an important food grain legume in the Sudano Sahelian zone of Mali. So far, an attention has not been addressed to the diversity of bradyrhizobia nodulating cowpea in this area. In order to fill this gap, effects of 3 cowpea varieties (IT89KD-374, CZ1-94-23-1 and CZ11-94-5C) on the diversity of native bradyrhizobia has been studied in 3 cropping systems from 2007 to 2008 at Cinzana Agronomic Research Station. The objective of the study was to identify effective bradyrhizobia strains nodulating cowpea and their impact on the intercropped or subsequent millet yield in the main cropping systems. Experimental design was a Randomized Complete Block Design using a factorial combination of 3 cowpea varieties and 3 cropping systems in 4 replications. PCR-RFLP and sequencing of the 16S - 23S of rDNA IGS were used to identify bradyrhizobia strains associated with cowpea varieties. Six IGS types have been identified. IGS type I (strain Bradyrhizobium sp.ORS 3642) was the most competitive regardless of cropping system and cowpea variety. The greater diversity averaged bradyrhizobia was found in variety IT89KD-374 (H' means = 0.39). Best millet grain yield in intercropped system (1520 kg ha-1) was obtained with cowpea variety IT89KD-374. The best above ground dry biomass production of subsequent millet (6 210 kg ha-1) has been obtained under CZ11- 94-5C - millet rotation. Types IGS IV and VI (ORS 3637 and STM 3378 strains respectively) appeared to be responsible for the performance of the Cowpea-millet rotation and cowpea variety CZ11-94-5C

Utilisation of wastewater for fuel and fodder production and environmental and social benefits in semi-arid, peri-urban zones of sub-Saharan Africa. Final Report 1/12/2002 - 30/11/2007 Contract number ICA4-CT-2002-10017

The overall objective was to develop low-tech water treatment and irrigation systems and test their use for the production of fuel wood and fodder in semi-arid sub-Saharan Africa. Sites for waste water treatment plants and irrigation systems were identified and the systems were constructed in Burkina Faso, Mali and Niger. Project partners were trained in how to use and maintain the systems. The irrigation sites were characterised in advance of tree planting, and soil and water analyses are being conducted regularly. Tree species with potential for use in irrigated conditions in each country were identified and experimental designs for the trials produced. Some species were used in common in all three countries. Nursery screening trials were conducted and plants were then planted at the irrigation sites. Trees grew quickly under the irrigated conditions and many species performed well. Species which were selected for their good performance in the nursery were not necessarily the best performers in the field. Biomass production was determined and the effects of different coppicing treatments on regrowth were assessed. Parameters of planting stock quality were assessed and incidence of pest attacks determined. Partners were also trained in the use of sap flow and associated equipment. Considerable variation between tree species in water use was noted, together with differential effects according to the inoculation history of the plants. Working in controlled glasshouse conditions, using sterilised soil media, considerable variation in effectiveness of different mycorrhizal strains on different tree species was detected. When plant response to simulated irrigation water was measured, uninoculated plants grew very poorly irrespective of whether they are receiving the simulated irrigation water or not. Thus mycorrhizal infection enabled plants to make use of the nutrients in the irrigation water. Initially, nursery and field studies gave much less clear results. However, assessments during the final year of the project demonstrated positive effects of inoculation on tree growth in Mali and Niger. These observations were reinforced on the rhizobial side by molecular studies, using strain-specific probes for nodule analysis. In Ouagadougou it was estimated that 225,004 tons of fuel wood and 6708 tons of charcoal per year are transported to the city. The average price of firewood was approximately 21 F CFA per kg, and charcoal was 60 – 110 F CFA per kg. Sellers can achieve a substantial income from sales. The large quantities of fuel imported into Ouagadougou highlight the pressure on fuel resources. This is further indicated by the observations in Niger and Mali. Dissemination to stakeholders has been conducted and is continuing. The irrigation sites are continuing to be run. An important development is the formation of a partnership with representative farmers’ organizations regrouped under the umbrella of ROPPA (Réseau des Organisations Paysannes et des Producteurs Agricoles d’Afrique de l’Ouest, who federates millions of farmers through twelve west African countries, with the objective of bringing symbionts to farmers