Phenotypic and genotypic characteristics ofAcacia senegal(L.) Willd. root-nodulating bacteria isolated from soils in the dryland part of Senegal

Abstract

Aims: We characterized phenotypically and genotypically root‐nodulating bacteria associated with Acacia senegal (L.) Willd. isolated from the soils surrounding A. senegal trees in the dry land area of Senegal. Methods and Results: The phenotypical and genotypical characterizations we carried out showed a high diversity of A. senegal root‐nodulating bacteria. Phenotypic patterns showed adaptations of the rhizobial strains to many environmental stresses such as heat, drought, and salinity. Twelve molecular groups were distinguished by profiles obtained using polymerase chain reaction/restriction fragment length polymorphism techniques from intergenic spacer region rDNA. The highest genetic diversity was found around the A. senegal rhizosphere. Therefore, A. senegal seemed to have a positive influence on occurrence and genotypical diversity of rhizobial populations. Rhizobial isolates obtained in this study belonged phylogenetically to the genera Mesorhizobium and Rhizobium. Conclusions: Our results provided information about the genetic diversity of the rhizobial strains associated with A. senegal and suggested the adaptability of natural rhizobial populations to major ecological environmental stress within these soil environments. Significance and Impact of the Study: These results suggested a potential selection of compatible and well adapted strains under stress conditions as inoculants for successful A. senegal growth in arid lands.

Diversity of new root nodule bacteria from Erythrina velutina Willd., a native legume from the Caatinga dry forest (Northeastern Brazil)

“…Other authors also confirmed the same tolerance characteristics of bacteria with the same growth characteristic (Zerhari et al, 2000;Fall et al, 2008;Rasul et al, 2012), which indicates that the studied mulungu isolates show a potential for inoculation in the semi-arid regions because they are well adapted to the typical stress conditions of these soils.…”

“…Phenotypic characterization is the basis of polyphasic taxonomy and, together with molecular techniques, has contributed to an improved understanding of the physiology and genetic diversity of rhizobia (Zerhari et al, 2000;Fall et al, 2008;Rasul et al, 2012). Among the molecular characterization techniques, fingerprinting by means of Box-PCR generated profiles have been used to examine the diversity of diazotrophic bacteria associated with the (Stocco et al, 2008;Costa et al, 2014;Torres-Júnior et al, 2014) and native species (Fernandes Júnior et al, 2013;Granada et al, 2014) from Brazil.…”

Distribution and Diversity of Rhizobial Populations Associated with <i>Acacia senegal</i> (L.) Willd. Provenances in Senegalese Arid and Semiarid Regions

“…Recently, numerical genotypic analyses revealed large genetic diversity among root-nodulating bacteria able to nodulate A. senegal (de Lajudie et al, 1998;Fall et al, 2008;Sarr et al, 2005a). However, these studies did not take into account various environmental conditions.…”

“…Nodules collected in situ (from Goudiry A. senegal plantation in August 2008) and in vitro were surface sterilized, isolated, and authenticated cultures preserved as described by Fall et al (2008). Polymerase chain reactions (PCR) were carried out, on the IGS rDNA of 42 isolates, directly on 2 µl of fresh bacterial culture suspended in 50 µl sterile water, and digested as described by Fall et al (2008).…”

“…Polymerase chain reactions (PCR) were carried out, on the IGS rDNA of 42 isolates, directly on 2 µl of fresh bacterial culture suspended in 50 µl sterile water, and digested as described by Fall et al (2008). Shannon diversity index was calculated according to Borcard & Buttler (2001).…”