Nodules of <i>Medicago</i> spp. Host a Diverse Community of Rhizobial Species in Natural Ecosystems
Andrei Stefan,
Jannick Van Cauwenberghe,
Craita Maria Rosu,
Catalina Stedel,
Crystal Chan,
Ellen L. Simms,
Catalina Iticescu,
Daniela Tsikou,
Emmanouil Flemetakis,
Rodica Catalina Efrose
Affiliations
Andrei Stefan
“Grigore Antipa” National Museum of Natural History, Șos. Kiseleff 1, 011341 Bucharest, Romania
Jannick Van Cauwenberghe
Institute of Biodiversity, Faculty of Biological Sciences, Cluster of Excellence Balance of the Microverse, Friedrich-Schiller-University Jena, 07743 Jena, Germany
Craita Maria Rosu
Department of Experimental and Applied Biology, NIRDBS-Institute of Biological Research Iași, Lascar Catargi 47, 700107 Iași, Romania
Catalina Stedel
Department of Experimental and Applied Biology, NIRDBS-Institute of Biological Research Iași, Lascar Catargi 47, 700107 Iași, Romania
Crystal Chan
Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
Ellen L. Simms
Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
Catalina Iticescu
Department of Chemistry, Physics and Environment, Faculty of Sciences and Environment, ‘Dunarea de Jos’ University of Galati, 800008 Galati, Romania
Daniela Tsikou
Department of Biochemistry and Biotechnology, University of Thessaly, Biopolis, 41500 Larissa, Greece
Emmanouil Flemetakis
Department of Biotechnology, Agricultural University of Athens, 75 Iera Odos Str., 11855 Athens, Greece
Rodica Catalina Efrose
Department of Experimental and Applied Biology, NIRDBS-Institute of Biological Research Iași, Lascar Catargi 47, 700107 Iași, Romania
Biological nitrogen fixation by rhizobia-nodulated legumes reduces the dependence on synthetic nitrogen fertilizers. Identification of locally adapted rhizobia may uncover economically valuable strains for sustainable agriculture. This study investigated the diversity and symbiotic potential of rhizobia associated with three Medicago species from Eastern Romania’s ecosystems. Phenotypic screening ensured that only rhizobial species were retained for molecular characterization. 16S rDNA sequencing clustered the isolates into four distinct groups: Sinorhizobium meliloti, Sinorhizobium medicae, Rhizobium leguminosarum, and Mesorhizobium spp. The chromosomal genes (atpD, glnII, recA) and nifH phylogenies were congruent, while the nodA phylogeny grouped the Mesorhizobium spp. isolates with R. leguminosarum. Medicago sativa was the most sampled plant species, and only S. meliloti and R. leguminosarum were found in its nodules, while Medicago falcata nodules hosted S. meliloti and Mesorhizobium spp. Medicago lupulina was the only species that hosted all four identified rhizobial groups, including S. medicae. This study provides the first report on the Mesorhizobium spp. associated with M. falcata nodules. Additionally, R. leguminosarum and two Mesorhizobium genospecies were identified as novel symbionts for Medicago spp. Comparative analysis of Medicago-associated rhizobia from other studies revealed that differences in 16S rDNA sequence type composition were influenced by Medicago species identity rather than geographic region.
