Phylogeographic distribution of rhizobia nodulating common bean (Phaseolus vulgaris L.) in Ethiopia

Abstract

Rhizobia are soil borne 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. R. etli and R. phaseoli 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 R. aethiopicum that was only isolated in the earlier collection.

Phylogenetic diversity and plant growth-promoting activities of rhizobia nodulating fenugreek (Trigonella foenum-graecumLinn.) cultivated in different agroclimatic regions of India

“…Several factors, including physico-chemical properties of soils and climatic conditions, are the key drivers of rhizobia distribution (Gehlot et al 2013;Lemaire et al 2015;Rathi et al 2018;de Castro Pires et al 2018;Gaci et al 2021). Alternatively, a few studies suggested the role of geography in the distribution of rhizobial genotypes (Rahi et al 2012;Zhang et al 2018), while some studies found no evidence for a geographic distribution (Gunnabo et al 2021a). See Sprent et al (2017) for a review.…”

Re-vegetation Improves Soil Quality by Decreasing Soil Conductivity and Altering Soil Microbial Communities: A Case Study of an Opencast Coal Mine in the Helan Mountains

“…In addition, soils re-vegetated by A. laxmannii showed higher soil nitrogen content. This could be due to the root nodules of A. laxmanni , whose commensal diazotrophs may provide a central source for increasing soil N content, as the nutrients in such soils are fixed in mineral forms, leading to low availability for plants ( Hailu Gunnabo et al, 2021 ). Nevertheless, our results provide evidence that re-vegetation increases soil quality by decreasing soil conductivity.…”

Potentials of underutilized legumes in food security

“…Likewise, the lablab bean's ability to associate with nitrogen-fixing rhizobia such as Mesorhizobium ensifer and Bradyrhizobium species has been reported (84). However, there could be variability in the nitrogen-fixing potentials of different rhizobia, for instance, Hailu Gunnabo et al (85) carried out research that revealed that of all the Rhizobium species isolated from the common bean in Ethiopia, only Rhizobium phaseoli and Rhizobium etli were predominant. This could be due to the ability to out-compete other organisms.…”