Systematic and Applied Microbiology 34 (2011) 368–375 Contents lists available at ScienceDirect Systematic and Applied Microbiology journal homepage: www.elsevier.de/syapm Bradyrhizobium canariense and Bradyrhizobium japonicum are the two dominant rhizobium species in root nodules of lupin and serradella plants growing in Europe Tomasz St ˛ epkowski a , Magdalena ˙ Zak a,c , Lionel Moulin b , Joanna Króliczak c , Barbara Goli ´ nska c , Dorota Naro ˙ zna c , Vera I. Safronova d , Cezary J. M ˛ adrzak c,∗ a Institute of Bioorganic Chemistry Polish Academy of Sciences, 61-704 Pozna´ n, Noskowskiego 12/14, Poland b IRD, UMR LSTM - Laboratoire des Symbioses Tropicales et Méditerranéennes, 34398 Montpellier cedex 5, France c Department of Biochemistry and Biotechnology, Poznan University of Life Sciences, 60-637 Poznan, Woly´ nska 35, Poland d All-Russia Research Institute for Agricultural Microbiology, Podbelskogo Sh.3, St.-Petersburg-Pushkin 196608, Russia article info Article history: Received 18 January 2011 Keywords: Bradyrhizobium Lupin noda gene Phylogeny Serradella abstract Forty three Bradyrhizobium strains isolated in Poland from root nodules of lupin species (Lupinus albus, L. angustifolius and L. luteus), and pink serradella (Ornithopus sativus) were examined based on phylogenetic analyses of three housekeeping (atpD, glnII and recA) and nodulation (nodA) gene sequences. Additionally, seven strains originating from root-nodules of yellow serradella (O. compressus) from Asinara Island (Italy) were included in this study. Phylogenetic trees revealed that 15 serradella strains, including all yellow serradella isolates, and six lupin strains grouped in Bradyrhizobium canariense (BC) clade, whereas eight strains from pink serradella and 15 lupin strains were assigned to Bradyrhizobium japonicum (BJ1). Apparently, these species are the two dominant groups in soils of central Europe, in the nodules of lupin and serradella plants. Only three strains belonged to other chromosomal lineages: one formed a cluster that was sister to B. canariense, one strain grouped outside the branch formed by B. japonicum super- group, and one strain occupied a distant position in the genus Bradyrhizobium, clustering with strains of the Rhodopseudomonas genus. All strains in nodulation nodA gene tree grouped in a cluster referred to as Clade II, which is in line with earlier data on this clade dominance among Bradyrhizobium strains in Europe. The nodA tree revealed four well-supported subgroups within Clade II (II.1–II.4). Interestingly, all B. canariense strains clustered in subgroup II.1 whereas B. japonicum strains dominated subgroups II.2–II.4. © 2011 Elsevier GmbH. All rights reserved. Introduction The genus Lupinus comprises some 275 species of annual and perennial herbs and shrubs, the majority of which are distributed in the New World, mainly in the western part of North America and the Andes. Only 15 species are native to the Old World, in areas surrounding the Mediterranean [1,16]. Lupins form highly effec- tive nitrogen-fixing symbiosis with root nodule bacteria often in nutrient-poor soils. This enables their cultivation in soils where growth of more demanding crops is difficult [19]. Lupins have been cultivated since the antiquity, mainly, as green manure and important pulse crop [12]. Three cultivated in Poland lupin species (Lupinus albus, L. angustifolius, L. luteus), as well as pink serradella (Ornithopus sativus) were introduced from southern Europe in the ∗ Corresponding author. Tel.: +48 61 848 7209; fax: +48 61 848 7211. E-mail address: madrzak@up.poznan.pl (C.J. M ˛ adrzak). first half of the XIX century. Extensive use of lupins as green manure was reported in the area around Pozna ´ n in 1840 [53]. In 1938, the area of 383,500 ha under lupins was recorded in Poland, whiles cul- tivation of serradella reached its peak in 1960 with 524,602 ha used for this legume crop. Since then the area under lupins and serradella declines constantly, so only about one tenth of it is used to grow this plants presently [13,53]. Lupins and serradella are nodulated by bacteria belonging to the genus Bradyrhizobium. Additionally, strains corresponding to other rhizobium genera inhabit lupin, but not serradella, nod- ules. These “fast growing” rhizobia, however, tend to form less effective nitrogen fixing symbiosis with lupin plants than bradyrhi- zobia [2,11,55]. Due to the highly specific symbiosis, serradella is often regarded as a surrogate hosts for lupins, which implies that serradella strains (all of which seem to belong to the genus Bradyrhizobium) nodulate lupins, whereas some lupin rhizobia are unable to infect serradella. Housekeeping gene phylogenies have revealed the considerable level of diversity among Bradyrhizo- 0723-2020/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.syapm.2011.03.002