Systematic and Applied Microbiology 32 (2009) 245–255 Retama species growing in different ecological–climatic areas of northeastern Algeria have a narrow range of rhizobia that form a novel phylogenetic clade within the Bradyrhizobium genus $ Boulila Farida a , Depret Ge ´ raldine b,c , Boulila Abdelghani a , Belhadi Djellali a , Benallaoua Said a , Laguerre Gise ` le d,e,f,g,h,Ã a Laboratoire de Microbiologie Applique´e, Faculte´des Sciences de la Nature et de la Vie, Universite´A. Mira, Be´jaı¨a, Algeria b INRA, UMR 1229 Microbiologie et Ge´ochimie des Sols, F-21065 Dijon, France c Universite´de Bourgogne, UMR 1229, F-21065 Dijon, France d USC INRA 1242-UMR 113 IRD-CIRAD-SupAgro-UM2, Laboratoire des Symbioses Tropicales et Me´diterrane´ennes, TA A-82/J Campus de Baillarguet, F-34398 Montpellier cedex 5, France e IRD, UMR 113 Symbioses Tropicales et Me´diterrane´ennes, F-34398 Montpellier, France f CIRAD, UMR 113 Symbioses Tropicales et Me´diterrane´ennes, F-34398 Montpellier, France g SupAgro, UMR 113 Symbioses Tropicales et Me´diterrane´ennes, F-34398 Montpellier, France h Universite´de Montpellier II, UMR 113 Symbioses Tropicales et Me´diterrane´ennes, F-34398 Montpellier, France Abstract Sixty-seven isolates were isolated from nodules collected on roots of Mediterranean shrubby legumes Retama raetam and Retama sphaerocarpa growing in seven ecological–climatic areas of northeastern Algeria. Genetic diversity of the Retama isolates was analyzed based on genotyping by restriction fragment length polymorphism of PCR-amplified fragments of the 16S rRNA gene, the intergenic spacer (IGS) region between the 16S and 23S rRNA genes (IGS), and the symbiotic genes nifH and nodC. Eleven haplotypes assigned to the Bradyrhizobium genus were identified. Significant biogeographical differentiation of the rhizobial populations was found, but one haplotype was predominant and conserved across the sites. All isolates were able to cross-nodulate the two Retama species. Accordingly, no significant genetic differentiation of the rhizobial populations was found in relation to the host species of origin. Sequence analysis of the 16S rRNA gene grouped the isolates with Bradyrhizobium elkanii, but sequence analyses of IGS, the housekeeping genes (dnaK, glnII, recA), nifH, and nodC yielded convergent results showing that the Retama nodule isolates from the northeast of Algeria formed a single evolutionary lineage, which was well differentiated from the currently named species or well-delineated unnamed genospecies of bradyrhizobia. Therefore, this study showed that the Retama species native to northeastern Algeria were associated with a specific clade of ARTICLE IN PRESS www.elsevier.de/syapm 0723-2020/$ - see front matter r 2009 Elsevier GmbH. All rights reserved. doi:10.1016/j.syapm.2009.01.005 $ Note: The nucleotide sequence data reported are available in the GenBank database under the following accession numbers: FJ264929–FJ26499 for the rDNA IGS; FJ264920–FJ264922 for dnaK; FJ264923–FJ264925 for glnII; FJ264926–FJ264928 for recA; FJ348667–FJ348678 for nifH; FJ348655–FJ348666 for nodC; FJ264919, FJ514036–FJ5141, and FJ546419 for the 16S rRNA gene. Ã Corresponding author at: USC INRA 1242-UMR 113 IRD-CIRAD-SupAgro-UM2, Laboratoire des Symbioses Tropicales et Me ´ diterra- ne ´ ennes, TA A-82/J Campus de Baillarguet, F-34398 Montpellier cedex 5, France. Tel.: +33 4 67 59 38 62; fax: +33 4 67 59 38 02. E-mail address: gisele.laguerre@supagro.inra.fr (L. Gise `le).