Symbiotic, phenotypic and genotypic characterization of Bradyrhizobium sp. nodulating Spartium junceum L. from Bejaia, northeastern Algeria Nacer Ramdani 1 & Djellali Belhadi 1 & Yahia Kaci 2 & Said Benallaoua 3 Received: 21 November 2019 /Accepted: 23 April 2020 # Springer Nature B.V. 2020 Abstract Twenty-three bacterial strains were isolated from root nodules of Spartium junceum L., growing wild in four distinct geographic locations in Bejaia city (Northeastern Algeria). They were analyzed based on their symbiotic effectiveness, phenotypic properties and restriction fragment length polymorphism of the 16S rRNA gene. In addition, sequence analyses of the ribosomal gene, protein-coding housekeeping genes glnII and recA, and symbiotic gene (nodC) were used to clarifying their taxonomic and phylogenetic position. Plant infection tests revealed that all strains were able to form nodules on their original host plant, but with variable nodulation ability and symbiotic effectiveness. All strains were slow-growing, alkali-producing rhizobia in YEMA medium. According to phenotypic test results, the strains were grouped in four main clusters in a UPGMA dendrogram, while they were discriminated into 12 distinct genotypes by 16S rDNA-RFLP. Phylogenetic analyses of 16S rRNA genes and two concatenated housekeeping genes, glnII and recA, distributed the representative strains from each RFLP genotypes into two major clades within Bradyrhizobium genus. Some of these strains were closely related to B. retamae and B. japonicum whereas others represented four novel genospecies. Based on analysis of the symbiotic gene sequence (nodC), all strains were placed in the symbiovar retamae cluster except for SjBA12 which possibly constitutes a new symbiovar within the genus Bradyrhizobium. Keywords Spartium junceum L. . Bradyrhizobium sp. . Symbiotic effectiveness . Phenotypic characterization . Phylogeny 1 Introduction Evergreen sclerophyllous plant communities especially le- gume shrubs, are common in the Mediterranean ecosystems as a result of their ability to adapt to the local climate of hot dry summers and cool, wet winters (Rodríguez-Echeverría et al. 2003; Blumler 2005). These shrubs are considered among the most successful pioneer plants as a result of their ability to rapidly colonize dry degraded areas, and thus often used to restore disturbed ecosystems (Valladares et al. 2002; Gómez-Aparicio et al. 2004 ; Gómez-Aparicio 2009; Busquets et al. 2010). Spanish Broom, Spartium junceum (L.), is one of these perennial shrubs native to the Mediterranean region from Southern Europe to Northwest Africa and Southwest Asia. (Angelini et al. 2000; Travlos et al. 2007). It has been introduced in many countries as a garden plant and used for soil erosion control (Bossard et al. 2000). S. junceum (L.) is the only species of the Spartium in the Genisteae tribe; and possesses xerophytic features that provide remarkable adaptability and resistance to drought and adverse environments (Preti and Giadrossich 2009). This shrub can grow vigorously in sunny areas from 0 to 1400 m above sea level (Pignatti 1982). It thrives quite well in arid regions with poor, dry and rocky soils (Busquets et al. 2010). Because of such characteristics, it is typically found in marginal soils, disturbed areas such as eroded, stony hillsides and roadsides (Preti and Giadrossich 2009; Sanhueza and Zalba 2012). Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13199-020-00679-8) contains supplementary material, which is available to authorized users. * Nacer Ramdani ramdani_nacer@hotmail.fr 1 Laboratoire d’Ecologie Microbienne, Faculté des Sciences de la Nature et de la Vie, Université de Bejaia, 06000 Bejaia, Algeria 2 Laboratoire de Biologie et Physiologie des Organismes, Faculté des Sciences Biologiques USTHB, BP 132 El Alia, Alger, Algeria 3 Laboratoire de Microbiologie Appliquée, Faculté des Sciences de la Nature et de la Vie, Université de Bejaia, 06000 Bejaia, Algeria Symbiosis https://doi.org/10.1007/s13199-020-00679-8