Abstract
ABSTRACTRhizobia are soilborne bacteria that form symbiotic relations with legumes and fix atmospheric nitrogen. The nitrogen fixation potential depends on several factors such as the type of host and symbionts and on environmental factors that affect the distribution of rhizobia. We isolated bacteria nodulating common bean in Southern Ethiopia to evaluate their genetic diversity and phylogeography at nucleotide, locus (gene/haplotype) and species levels of genetic hierarchy. Phylogenetically, eight rhizobial genospecies (including previous collections) were determined that had less genetic diversity than found among reference strains. The limited genetic diversity of the Ethiopian collections was due to absence of many of the Rhizobium lineages known to nodulate beans. Rhizobium etli and Rhizobiumphaseoli were predominant strains of bean-nodulating rhizobia in Ethiopia. We found no evidence for a phylogeographic pattern in strain distribution. However, joint analysis of the current and previous collections revealed differences between the two collections at nucleotide level of genetic hierarchy. The differences were due to genospecies Rhizobium aethiopicum that was only isolated in the earlier collection.
Highlights
Common bean (Phaseolus vulgaris L.) nodulates with soil bacteria, collectively known as rhizobia, that fix atmospheric nitrogen in symbiosis with their host
We show that there is high genetic diversity within clades but less variation among overall rhizobia nodulating common bean growing in Ethiopia compared with that described from other parts of the world
The R. etli genospecies is more diverse than the R. phaseoli genospecies among the Ethiopian bean rhizobia, suggesting either faster sequence divergence within the R. etli genospecies, random introduction of R. etli and R. phaseoli, or a genetic bottleneck in R. phaseoli
Summary
Common bean (Phaseolus vulgaris L.) nodulates with soil bacteria, collectively known as rhizobia, that fix atmospheric nitrogen in symbiosis with their host. It is grown across a wide range of environments—at elevations ranging from 800 to 2200 m.a.s.l in Southern Ethiopia (Asfaw 2011) and on a wide range of soil types (Asfaw et al 2009). It is thereby possible that some common bean growing environments or locations lack effective rhizobia, leading to unproductive symbiosis and poor fixation, while localized differences in either competitiveness or effectiveness could lead to varying inoculation responses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
