Rhizobia 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.

中文翻译：

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埃塞俄比亚结瘤菜豆（Phaseolus vulgaris L.）的系统发育地理分布


根瘤菌是土传细菌，与豆科植物形成共生关系并固定大气中的氮。固氮潜力取决于多种因素，例如宿主和共生体的类型以及影响根瘤菌分布的环境因素。我们在埃塞俄比亚南部分离了普通豆结瘤细菌，以评估它们在核苷酸、基因座（基因/单倍型）和遗传层次的物种水平上的遗传多样性和系统发育地理学。在系统发育上，确定了八个根瘤菌基因种（包括以前的收集品），其遗传多样性低于参考菌株中的遗传多样性。埃塞俄比亚收集品的遗传多样性有限是由于缺乏许多已知使豆类结瘤的根瘤菌谱系。 Rhizobium etli 和Rhizobiumphaseoli 是埃塞俄比亚豆结瘤根瘤菌的主要菌株。我们没有发现菌株分布中系统发育地理模式的证据。然而，对当前和以前收藏品的联合分析揭示了两个收藏品在遗传层次的核苷酸水平上的差异。差异是由于仅在早期收集中分离出的基因种埃塞俄比亚根瘤菌所致。