title: Rhizobia Indigenous to the Okavango Region in Sub-Saharan Africa: Diversity, Adaptations, and Host Specificity.
abstract: The rhizobial community indigenous to the Okavango region has not yet been characterized. The isolation of indigenous rhizobia can provide a basis for the formulation of a rhizobial inoculant. Moreover, their identification and characterization contribute to the general understanding of species distribution and ecology. Isolates were obtained from nodules of local varieties of the pulses cowpea, Bambara groundnut, peanut, hyacinth bean, and common bean. Ninety-one of them were identified by BOX repetitive element PCR (BOX-PCR) and sequence analyses of the 16S-23S rRNA internally transcribed spacer (ITS) and the recA, glnII, rpoB, and nifH genes. A striking geographical distribution was observed. Bradyrhizobium pachyrhizi dominated at sampling sites in Angola which were characterized by acid soils and a semihumid climate. Isolates from the semiarid sampling sites in Namibia were more diverse, with most of them being related to Bradyrhizobium yuanmingense and Bradyrhizobium daqingense. Host plant specificity was observed only for hyacinth bean, which was nodulated by rhizobia presumably representing yet-undescribed species. Furthermore, the isolates were characterized with respect to their adaptation to high temperatures, drought, and local host plants. The adaptation experiments revealed that the Namibian isolates shared an exceptionally high temperature tolerance, but none of the isolates showed considerable adaptation to drought. Moreover, the isolates' performance on different local hosts showed variable results, with most Namibian isolates inducing better nodulation on peanut and hyacinth bean than the Angolan strains. The local predominance of distinct genotypes implies that indigenous strains may exhibit a better performance in inoculant formulations.
authors.affiliation: Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen (CBIB), University of Bremen, Bremen, Germany.
authors.forename: Jann L
authors.initials: JL
authors.lastname: Grönemeyer
authors.affiliation: Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen (CBIB), University of Bremen, Bremen, Germany.
authors.forename: Ajinkya
authors.initials: A
authors.lastname: Kulkarni
authors.affiliation: Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen (CBIB), University of Bremen, Bremen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Berkelmann
authors.affiliation: Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen (CBIB), University of Bremen, Bremen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hurek
authors.affiliation: Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen (CBIB), University of Bremen, Bremen, Germany breinhold@uni-bremen.de.
authors.forename: Barbara
authors.initials: B
authors.lastname: Reinhold-Hurek
mesh_terms: D017954:Africa South of the Sahara; D001426:Bacterial Proteins / Q000235:genetics; D044822:Biodiversity; D020369:Bradyrhizobium / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D012321:DNA-Directed RNA Polymerases; D058507:Host Specificity; D008969:Molecular Sequence Data; D058974:Phylogeography; D010944:Plants / Q000382:microbiology; D053204:Root Nodules, Plant / Q000382:microbiology*; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit