title: Phenotypic and genetic characterization of rhizobia associated with alfalfa in the Hokkaido and Ishigaki regions of Japan.
abstract: Twenty five rhizobial isolates were obtained from root nodules of Medicago sativa inoculated with soil samples collected from the Sapporo region and Ishigaki Island in Japan. To study their diversity and characterize them in relation to the climatic conditions of their soils of origin, a polyphasic approach analyzing stress tolerance, symbiotic and genetic properties was used. Stress tolerance assays revealed marked variations in salinity, pH and temperature tolerance. Isolates originating from a sub-tropical climate in alkaline soil (Ishigaki Island) tolerated high temperature, salinity and pH levels. Moreover, isolates recovered from a temperate climate in acidic soil (Sapporo) were sensitive to high temperature and salinity, and tolerated acidic pH. Phylogenetic analysis of conserved 16S rRNA and recA genes, and symbiotic nodA and nifDK revealed 25 isolates to be closely related to Ensifer meliloti. Furthermore, the branch patterns of phylogenetic trees constructed from different genes revealed the existence of at least two E. meliloti types in the soils studied. These results may be relevant to programs directed towards improving crop productivity through biofertilization with locally adapted and genetically defined strains.
authors.affiliation: United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
authors.forename: Salem
authors.initials: S
authors.lastname: Djedidi
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Norihiko
authors.initials: N
authors.lastname: Tomooka
authors.forename: Naoko
authors.initials: N
authors.lastname: Ohkama-Ohtsu
authors.forename: Chandra Prasad
authors.initials: CP
authors.lastname: Risal
authors.forename: Chedly
authors.initials: C
authors.lastname: Abdelly
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sekimoto
mesh_terms: D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D007564:Japan; D000455:Medicago sativa / Q000382:microbiology*; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D012231:Rhizobium / Q000145:classification* / Q000235:genetics; D053204:Root Nodules, Plant / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013559:Symbiosis / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S