The genetic diversity of bacterial populations nodulating Lupinus micranthus in five geographical sites from northern Tunisia was examined. Phylogenetic analyses of 50 isolates based on partial sequences of recA and gyrB grouped strains into seven clusters, five of which belong to the genus Bradyrhizobium (28 isolates), one to Phyllobacterium (2 isolates), and one, remarkably, to Microvirga (20 isolates). The largest Bradyrhizobium cluster (17 isolates) grouped with the B. lupini species, and the other five clusters were close to different recently defined Bradyrhizobium species. Isolates close to Microvirga were obtained from nodules of plants from four of the five sites sampled. We carried out an in-depth phylogenetic study with representatives of the seven clusters using sequences from housekeeping genes (rrs, recA, glnII, gyrB, and dnaK) and obtained consistent results. A phylogeny based on the sequence of the symbiotic gene nodC identified four groups, three formed by Bradyrhizobium isolates and one by the Microvirga and Phyllobacterium isolates. Symbiotic behaviors of the representative strains were tested, and some congruence between symbiovars and symbiotic performance was observed. These data indicate a remarkable diversity of L. micranthus root nodule symbionts in northern Tunisia, including strains from the Bradyrhizobiaceae, Methylobacteriaceae, and Phyllobacteriaceae families, in contrast with those of the rhizobial populations nodulating lupines in the Old World, including L. micranthus from other Mediterranean areas, which are nodulated mostly by Bradyrhizobium strains.IMPORTANCE Lupinus micranthus is a legume broadly distributed in the Mediterranean region and plays an important role in soil fertility and vegetation coverage by fixing nitrogen and solubilizing phosphate in semiarid areas. Direct sowing to extend the distribution of this indigenous legume can contribute to the prevention of soil erosion in pre-Saharan lands of Tunisia. However, rhizobial populations associated with L. micranthus are poorly understood. In this context, the diversity of endosymbionts of this legume was investigated. Most Lupinus species are nodulated by Bradyrhizobium strains. This work showed that about half of the isolates from northern Tunisian soils were in fact Bradyrhizobium symbionts, but the other half were found unexpectedly to be bacteria within the genera Microvirga and Phyllobacterium. These unusual endosymbionts may have a great ecological relevance. Inoculation with the appropriate selected symbiotic
The genetic diversity of bacterial populations nodulating Lupinus luteus (yellow lupine) in Northern Tunisia was examined. Phylogenetic analyses of 43 isolates based on recA and gyrB partial sequences grouped them in three clusters, two of which belong to genus Bradyrhizobium (41 isolates) and one, remarkably, to Microvirga (2 isolates), a genus never previously described as microsymbiont of this lupine species. Representatives of the three clusters were analysed in-depth by multilocus sequence analysis of five housekeeping genes (rrs, recA, glnII, gyrB and dnaK). Surprisingly, the Bradyrhizobium cluster with the two isolates LluI4 and LluTb2 may constitute a new species defined by a separate position between Bradyrhizobium manausense and B. denitrificans. A nodC-based phylogeny identified only two groups: one formed by Bradyrhizobium strains included in the symbiovar genistearum and the other by the Microvirga strains. Symbiotic behaviour of representative isolates was tested, and among the seven legumes inoculated only a difference was observed i.e. the Bradyrhizobium strains nodulated Ornithopus compressus unlike the two strains of Microvirga. On the basis of these data, we conclude that L. luteus root nodule symbionts in Northern Tunisia are mostly strains within the B. canariense/B. lupini lineages, and the remaining strains belong to two groups not previously identified as L. luteus endosymbionts: one corresponding to a new clade of Bradyrhizobium and the other to the genus Microvirga.
Thirty-two bacterial isolates were obtained from root nodules of Lupinus angustifolius growing in Northern Tunisia. Phylogenetic analyses based on recA and gyrB partial gene sequences grouped the strains into six clusters: four clusters belonged to the genus Bradyrhizobium (22 isolates), one to Microvirga (8 isolates) and one to Devosia (2 isolates), a genus that has not been previously reported to nodulate lupin. Representative strains of each group were further characterized. Multi-Locus Sequence Analysis (MLSA) based on recA and glnII gene sequences separated the strains within the genus Bradyrhizobium into four divergent clusters related to B. canariense, B. liaoningense, B. lupini, and B. algeriense, respectively. The latter might constitute a new Bradyrhizobium species. The strains in the Microvirga cluster showed high identity with M. tunisiensis. The Devosia isolates might also represent a new species within this genus. An additional phylogenetic analysis based on the symbiotic gene nodC affiliated the strains to symbiovars genistearum, mediterranense, and to a possibly new symbiovar. These results altogether contributed to the existing knowledge on the genetic diversity of lupin-nodulating microsymbionts and revealed a likely new, fast-growing, salt-tolerant rhizobial species within the genus Devosia as a potentially useful inoculant in agricultural practices or landscape restoration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.