title: Phylogeny of nodulation genes and symbiotic diversity of Acacia senegal (L.) Willd. and A. seyal (Del.) Mesorhizobium strains from different regions of Senegal.
abstract: Acacia senegal and Acacia seyal are small, deciduous legume trees, most highly valued for nitrogen fixation and for the production of gum arabic, a commodity of international trade since ancient times. Symbiotic nitrogen fixation by legumes represents the main natural input of atmospheric N2 into ecosystems which may ultimately benefit all organisms. We analyzed the nod and nif symbiotic genes and symbiotic properties of root-nodulating bacteria isolated from A. senegal and A. seyal in Senegal. The symbiotic genes of rhizobial strains from the two Acacia species were closed to those of Mesorhizobium plurifarium and grouped separately in the phylogenetic trees. Phylogeny of rhizobial nitrogen fixation gene nifH was similar to those of nodulation genes (nodA and nodC). All A. senegal rhizobial strains showed identical nodA, nodC, and nifH gene sequences. By contrast, A. seyal rhizobial strains exhibited different symbiotic gene sequences. Efficiency tests demonstrated that inoculation of both Acacia species significantly affected nodulation, total dry weight, acetylene reduction activity (ARA), and specific acetylene reduction activity (SARA) of plants. However, these cross-inoculation tests did not show any specificity of Mesorhizobium strains toward a given Acacia host species in terms of infectivity and efficiency as stated by principal component analysis (PCA). This study demonstrates that large-scale inoculation of A. senegal and A. seyal in the framework of reafforestation programs requires a preliminary step of rhizobial strain selection for both Acacia species.
authors.affiliation: Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP de Dakar, BP 5005, Dakar, Senegal, niokhor.bakhoum@gmail.com.
authors.forename: Niokhor
authors.initials: N
authors.lastname: Bakhoum
authors.forename: Antoine
authors.initials: A
authors.lastname: Galiana
authors.forename: Christine
authors.initials: C
authors.lastname: Le Roux
authors.forename: Aboubacry
authors.initials: A
authors.lastname: Kane
authors.forename: Robin
authors.initials: R
authors.lastname: Duponnois
authors.forename: Fatou
authors.initials: F
authors.lastname: Ndoye
authors.forename: Dioumacor
authors.initials: D
authors.lastname: Fall
authors.forename: Kandioura
authors.initials: K
authors.lastname: Noba
authors.forename: Samba Ndao
authors.initials: SN
authors.lastname: Sylla
authors.forename: Diégane
authors.initials: D
authors.lastname: Diouf
mesh_terms: D000045:Acacia / Q000382:microbiology*; D000217:Acyltransferases / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D059128:Mesorhizobium / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics* / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D053204:Root Nodules, Plant / Q000382:microbiology; D012675:Senegal; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D010088:Oxidoreductases; C029130:nitrogenase reductase; D000217:Acyltransferases; C060770:NodA protein, Rhizobiales; D017351:N-Acetylglucosaminyltransferases; C060771:NodC protein, Rhizobiales