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Pule-Meulenberg F.,Tshwane University of Technology | Belane A.K.,Tshwane University of Technology | Krasova-Wade T.,Laboratoire Communications Of Microbiologie Lcm Ird Isra Ucad | Dakora F.D.,Tshwane University of Technology
BMC Microbiology | Year: 2010

Background: Cowpea is the most important food grain legume in Sub-Saharan Africa. However, no study has so far assessed rhizobial biodiversity and/or nodule functioning in relation to strain IGS types at the continent level. In this study, 9 cowpea genotypes were planted in field experiments in Botswana, South Africa and Ghana with the aim of i) trapping indigenous cowpea root-nodule bacteria (cowpea "rhizobia") in the 3 countries for isolation, molecular characterisation using PCR-RFLP analysis, and sequencing of the 16S - 23S rDNA IGS gene, ii) quantifying N-fixed in the cowpea genotypes using the 15N natural abundance technique, and iii) relating the levels of nodule functioning (i.e. N-fixed) to the IGS types found inside nodules. Results. Field measurements of N2fixation revealed significant differences in plant growth, 15N values, %Ndfa and amounts of N-fixed between and among the 9 cowpea genotypes in Ghana and South Africa. Following DNA analysis of 270 nodules from the 9 genotypes, 18 strain IGS types were found. Relating nodule function to the 18 IGS types revealed significant differences in IGS type N2-fixing efficiencies. Sequencing the 16S - 23S rDNA gene also revealed 4 clusters, with cluster 2 forming a distinct group that may be a new Bradyrhizobium species. Taken together, our data indicated greater biodiversity of cowpea bradyrhizobia in South Africa relative to Botswana and Ghana. Conclusions. We have shown that cowpea is strongly dependant on N2fixation for its N nutrition in both South Africa and Ghana. Strain IGS type symbiotic efficiency was assessed for the first time in this study, and a positive correlation was discernible where there was sole nodule occupancy. The differences in IGS type diversity and symbiotic efficiency probably accounts for the genotype × environment interaction that makes it difficult to select superior genotypes for use across Africa. The root-nodule bacteria nodulating cowpea in this study all belonged to the genus Bradyrhizobium. Some strains from Southern Africa were phylogenetically very distinct, suggesting a new Bradyrhizobium species. © 2010 Pule-Meulenberg et al; licensee BioMed Central Ltd.

Sene G.,Laboratoire Communications Of Microbiologie Lcm Ird Isra Ucad | Sene G.,Institute Senegalais Of Recherches Agricoles | Thiao M.,Cheikh Anta Diop University | Mbaye R.S.,Laboratoire Communications Of Microbiologie Lcm Ird Isra Ucad | And 8 more authors.
African Journal of Microbiology Research | Year: 2010

The aim of this investigation was to isolate the most specific, effective and competitive strains for peanut, and to determine the level of variability in peanut cultivars response toward single/dual inoculation. Peanut seeds of three cultivars namely 55-437, Fleur 11 and 69-101 were inoculated with two bradyrhizobial strains (LMG9283 and USDA3187) and an AM fungus Glomus intraradices, individually or in combination, and were grown in the open-air conditions using a non-sterile sandy soil from Sangalkam. Plant controls were supplied with NPK chemical fertilizer at the rate of 150 and 300 kg ha-1. Results obtained in term of nodule occupancy revealed a high competitiveness of LMG9283 strain with cultivars 55-437 and 69-101. However Fleur 11 cultivar was nodulated by indigenous strains rather than the introduced strains. Assessment of the data on nodulation, shoot biomass and pods yield revealed that, among the single inoculation of the three cultivars, 55-437 and 69-101 produced the largest increase in the parameters studied, however, Fleur 11 showed a higher growth and pods yield with the chemical fertilization. The dual inoculation with bradyrhizobial strains associated with G. intraradices further improved the parameters studied for 55-437 and 69-101, demonstrating a synergy between LMG9283 and G. intraradices. This better response allowed us to suggest that 55-437 and 69- 101 cultivars should be tested in the arable fields with Bradyrhizobium strain LMG9283 and G. intraradices. ©2010 Academic Journals.

Sene G.,Laboratoire Communications Of Microbiologie Lcm Ird Isra Ucad | Sene G.,Institute Senegalais Of Recherches Agricoles | Samba-Mbaye R.,Laboratoire Communications Of Microbiologie Lcm Ird Isra Ucad | Samba-Mbaye R.,Cheikh Anta Diop University | And 9 more authors.
European Journal of Soil Biology | Year: 2012

Exotic and native tree species have been widely used in the West Africa to reverse the tendency of land degradation. Although benefic effects have been reported on soil stabilization, a lack of information about their impact on soil symbiotic microorganisms still remains. This investigation has been carried out in a semiarid Sahel region and aimed to survey the abundance and diversity of natural legume-nodulating rhizobia (LNR) and arbuscular mycorrhizal (AM) fungal communities in soil samples from deforested and man-made forest systems. A genetically diverse LNR population is supported by the phylogenetic analysis, which clustered the isolates into three genera: Bradyrhizobium, Mesorhizobium and Sinorhizobium. The results showed that the man-made forest systems increased the LNR abundance and genetic diversity as well as the soil phosphorus and nitrogen contents. By contrast, strong modifications have been recorded in the characteristics of the AM fungal communities. The number of AM fungus taxa as well as the mycorrhizal inoculum potential (MIP) of soils decreased drastically in the man-made forest systems in comparison with the deforested land. In addition, the larger-spored AM fungi (Scutellospora and Gigaspora) were specifically found in soil samples from the deforested land. The displacement of larger-spored species was associated with a concomitant proliferation of small spored (Glomus) species. We conclude that man-made forestry can modify the soil symbiotic microorganisms and the results support the need for further adoption of management practices that could improve or sustain the development of herbaceous layers to promote the soil AM fungal communities. © 2012 Elsevier Masson SAS.

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