Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain.
Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Salamanca, Spain; Instituto de Investigación Biomédica de Salamanca (IBSAL), Complejo Asistencial Universitario de Salamanca, Universidad de Salamanca, CSIC, Salamanca, Spain.
Syst Appl Microbiol. 2023 Sep;46(5):126454. doi: 10.1016/j.syapm.2023.126454. Epub 2023 Sep 4.
Cajanus cajan L. (guandul) is commonly cultivated in Dominican Republic where this legume is a subsistence crop. Here we identified through MALDI-TOF MS several rhizobial strains nodulating C. cajan in two Dominican locations as Bradyrhizobium yuanmingense. The phylogenetic analysis of recA and glnII housekeeping genes showed that these strains belong to a wide cluster together with the type strain of B. yuanmingense and other C. cajan nodulating strains previously isolated in Dominican Republic. The comparison of genomes from strains representative of different lineages within this cluster support the existence of several genospecies within B. yuanmingense, which is the major microsymbiont of C. cajan in Dominican Republic where it is also nodulated by Bradyrhizobium cajani and Bradyrhizobium pachyrhizi. The analysis of the symbiotic nodC gene showed that the C. cajan nodulating strains from the B. yuanmingense complex belong to two clusters with less than 90% similarity between them. The strains from these two clusters showed nodC gene similarity values lower than 90% with respect to the remaining Bradyrhizobium symbiovars and then they correspond to two new symbiovars for which we propose the names americaense and caribense. The results of the nodC gene analysis also showed that C. cajan is nodulated by the symbiovar tropici, which has been found by first time in this work within the species Bradyrhizobium pachyrhizi. These results confirmed the high promiscuity degree of C. cajan, which is also nodulated by the symbiovar cajani of Bradyrhizobium cajani in Dominican Republic.
落花生（guandul）在多米尼加共和国广泛种植，是一种生计作物。我们通过 MALDI-TOF MS 鉴定出在多米尼加共和国的两个地点，有几种根瘤菌菌株可以与落花生共生，它们被鉴定为慢生根瘤菌（Bradyrhizobium yuanmingense）。recA 和 glnII 看家基因的系统发育分析表明，这些菌株属于一个广泛的聚类，与慢生根瘤菌的模式菌株以及之前在多米尼加共和国分离到的其他与落花生共生的菌株聚在一起。对来自该聚类中不同谱系的菌株基因组的比较支持在慢生根瘤菌中存在几个种下分类单元，它是多米尼加共和国落花生的主要微共生体，也被巴西固氮根瘤菌（Bradyrhizobium cajani）和中慢生根瘤菌（Bradyrhizobium pachyrhizi）所共生。共生 nodC 基因的分析表明，来自慢生根瘤菌复合群的落花生共生菌株属于两个聚类，它们之间的相似度小于 90%。这两个聚类中的菌株与其余的慢生根瘤菌共生型的 nodC 基因相似度值低于 90%，因此它们对应于两个新的共生型，我们建议将它们分别命名为 americaense 和 caribense。nodC 基因分析的结果还表明，落花生被热带根瘤菌（symbiovar tropici）所共生，这是首次在中慢生根瘤菌（Bradyrhizobium pachyrhizi）中发现该共生型。这些结果证实了落花生高度的混杂性，它在多米尼加共和国也被巴西固氮根瘤菌（Bradyrhizobium cajani）的 symbiovar cajani 所共生。
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