Distribution and Diversity of Rhizobial Populations Associated with &amp;lt;i&amp;gt;Acacia senegal&amp;lt;/i&amp;gt; (L.) Willd. Provenances in Senegalese Arid and Semiarid Regions

Niokhor Bakhoum,Kandioura Noba,Dioumacor Fall,Samba Ndao Sylla,Antoine Galiana,Aboubakry Kane,Diégane Diouf,Christine Le Roux,Robin Duponnois,Fatou Ndoye

doi:10.4236/ojf.2014.42019

Abstract

Abstract: Distribution and diversity of rhizobial strains associated with Acacia senegal (L.) Willd. in relation to seed provenances in soils from arid (Dahra) and semiarid (Goudiry) zones of Senegal were investigated. PCR-RFLP performed on 16S-23S rDNA intergenic spacer (IGS) of nodule crude extracts revealed a high genetic diversity of rhizobial strains, which was higher in the semiarid region than in the arid region. The distribution of rhizobial populations was influenced by soil physical and chemical characteristics, and by A. senegal provenances as shown by the analysis of correspondence. In contrast, the phenotypic diversity of rhizobial strains was not correlated with the soil origin. The phylogenetic tree (performed by the maximum likelihood algorithm) of IGS 16S-23S sequences showed that most of the rhizobial strains nodulating A. senegal were closely related to Mesorhizobium plurifarium. Our results showed that rhizobial taxa associated with A. senegal were mainly distributed according to soil physical and chemical characteristics, and A. senegal provenances. A large subset of A. senegal root-nodulating bacteria had high diversity that correlated with the most favourable environmental conditions. Understanding the diversity and distribution of rhizobial strains may be exploited in the formulation of A. senegal inoculants for different seed provenances for resilience to soil stresses in various environmental conditions.

Highlights

Many legume trees significantly contribute to the nitrogen balance of tropical wetlands and rainforests (Dommergues, 1995; Pons et al, 2007; Roggy et al, 1999), and play an important role in their function and ecology
The distribution of root-nodulating bacteria associated with A. senegal was correlated to physical and chemical characteristics of the soils
The root-nodulating bacteria associated to A. senegal seemed to be selected by the seed provenance

Summary

Introduction

Many legume trees significantly contribute to the nitrogen balance of tropical wetlands and rainforests (Dommergues, 1995; Pons et al, 2007; Roggy et al, 1999), and play an important role in their function and ecology. The prevalence of legumes to inhabit different environmental conditions might be related to their ability to associate with rhizobia, which enable them to fix atmospheric nitrogen (Moreira et al, 1992). Among these legumes, A. senegal is a species of major importance for the reforestation of arid and semiarid zones in sub-Saharian Africa. A. senegal is a species of major importance for the reforestation of arid and semiarid zones in sub-Saharian Africa This multipurpose species is much valued by rural populations as a source of fodder and timber, and gum arabic (Muller & Okoro, 2004). Diversity is of major importance in the function of root nodulating communities by imparting greater resilience to soil stresses (Bala & Giller, 2007). Keyser et al (1993) reported that the efficient exploitation of biological nitrogen fixation to improve agricultural productivity required the characterization and isolation of a population of native rhizobia

Methods

Results

Conclusion