Abstract：
The symbiovar mediterranense of Sinorhizobium meliloti was initially found in Phaseolus vulgaris nodules in Tunisia and in an eastern location of Lanzarote (Canary Islands). Here we show that the symbiovar mediterranense of S. meliloti also nodulates P. vulgaris in two western locations of this Island. The analyses of the symbiotic nodA and nodC genes reveal the complexity of the symbiovar mediterranense which encompasses strains belonging to several phylogenetic lineages and clusters. The comparison of the nodA and nodC phylogenies showed that the nodC was the most resolutive phylogenetic marker for the delineation of Sinorhizobium symbiovars. Considering that the similarity of this gene within several symbiovars, particularly mediterranense, is around 95 %, the cut-off value for their differentiation should be lower. Considering that a nodC gene cut-off similarity value of around 92 % is accepted for the genus Bradyrhizobium and that the symbiovar concept is identical in all rhizobial genera, we propose to apply this value for symbiovars delineation within all these genera. Therefore, using this cut-off value for the nodC gene analysis of Sinorhizobium symbiovars, we propose to merge the symbiovars aegeanense and fredii into the single symbiovar fredii and to define four novel symbiovars with the names asiaense, culleni, sudanense and tunisiaense.
摘要：
最初在突尼斯的菜豆结核和兰萨罗特岛（加那利群岛）的东部地区发现了中华根瘤菌的共生中间生物。在这里，我们显示了S.meliloti的共生中质也使该岛西部两个地区的寻常型假单胞菌结瘤。对共生nodA和nodC基因的分析揭示了共生中间生物的复杂性，其中包括属于几个系统发育谱系和簇的菌株。nodA和nodC系统发育的比较表明，nodC是区分中华根瘤菌共生的最确定的系统发育标记。考虑到这个基因在几个共生中的相似性，尤其是地中海，大约是95%，其差异化的临界值应该更低。考虑到缓生根瘤菌属的nodC基因截止相似度值约为92％，并且所有根瘤菌属的共生概念都相同，我们建议将该值应用于所有这些属中的共生描述。因此,利用这个临界值对中华根瘤菌共生菌的nodC基因进行分析，我们建议将共生体aegeanense和fredii合并为单个共生体fredii，并定义四个名为asiaense的新共生体，Culleni,苏丹和突尼斯。
