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.

Isolation and molecular identification of endophytic diazotrophs from seeds and stems of three cereal crops

“…The nifH gene is very important to biological nitrogen fixation which encodes nitrogen reductase of the nitrogenase, and it can be used as a nitrogen fixing tag. Nodulation (nod) genes which encode Nod factors contain a lot of nodule related genes, among them nodA and nodC as molecular markers of nitrogen fixing bacteria are important to nodules [ 28 ]. In the study, about 300-bp nifH gene fragments ( Fig 1a ) were obtained from the ten isolates, however, there were not nodA genes in the ten bacteria.…”

Faba Bean (Vicia faba L.) Nodulating Rhizobia in Panxi, China, Are Diverse at Species, Plant Growth Promoting Ability, and Symbiosis Related Gene Levels

“…In the present study, nifH gene that is the structural gene encoding the nitrogenase Fe protein (Masson-Boivin et al, 2009 ), and nodC that is the gene encoding enzymes involved in the synthesis of the core structure of the Nod-factor (Geremia et al, 1994 ) were selected for sequencing to analyze the symbiotic phylogeny of the faba bean rhizobia in Panxi region. The symbiotic genes are commonly located on a symbiotic plasmid or island which may be transferred (Laranjo et al, 2012 ; Bakhoum et al, 2014 ). Faba bean nodulating R. leguminosarum strains that carried four different types of nodulation gene nodD had all similar nodC (Table 4 ) (Tian et al, 2007 ).…”

Senegalia Senegal response to inoculation with rhizobial strains vary in relation to seed provenance and soil type

“…They were all isolated from S. senegal in Senegal and selected on the basis of their symbiotic infectivity and effectiveness (Bakhoum et al 2012;Fall et al 2008;Sarr et al 2005b). S. senegal nodulating rhizobial strains used in this study have identical nodA, nodC, and nifH gene sequences, and are closely related to Mesorhizobium plurifarium (Bakhoum et al 2015;Fall et al 2008).…”