Genetic Diversity in Bradyrhizobium japonicum Serogroup 123 and Its Relation to Genotype-Specific Nodulation of Soybean

Abstract

The genetic diversity among 20 field isolates of Bradyrhizobium japonicum serogroup 123 was examined by using restriction endonuclease digestions, one-dimensional sodium dodecyl sulfate-polyacrylamide gel electro-phQresis of total cell proteins, Southern hybridization analysis of nif and nod genes, and intrinsic antibiotic resistance profiles. All of the isolates were previously separated into three broad nodulation classes (low, medium, and high) based on their ability to form symbioses with specific soybean genotypes. Results of our studies indicate that there is a relationship between these three genotype-specific nodulation classes and groupings that have been made based on genomic DNA digestion patterns, sodium dodecyl sulfate-protein profiles, and Southern hybridizations to a nipHD gene probe. Intrinsic antibiotic resistance profiles and nodAB gene hybridizations were not useful in determining interrelationships between isolates and nodulation classes. Southern hybridizations revealed that two of the isolates had reiterated nod genes; however, there was no correlation between the presence of extra nodAB genes and the nodulation classes or symbiotic performance on permissive soybean genotypes. Hybridizations with the nif gene probe indicated that there is a relationship among serogroup, nodulation class, and the physical organization of the genome.

Enumeration of Soybean‐Associated Rhizobia with Quantitative Real‐Time Polymerase Chain Reaction

“…Reactions were separated with a 1.5% agarose gel. Cultures used for primer testing were maintained on plates with solid arabinose-gluconate growth media (Sadowsky et al, 1987). Before DNA extraction, one colony was harvested and grown in 5 mL of liquid AG on a dark, 28°C shaker overnight.…”

Predominant populations of indigenous soybean-nodulating Bradyrhizobium japonicum strains obtained from organic farming systems in Minnesota

“…Surface-sterilized nodules were washed with eight changes of sterile, distilled water and each nodule was placed individually into 100 ll of 0Á85% NaCl in wells of microtitre plates. Nodules were crushed with a sterile loop and streaked onto the surface of arabinose-gluconate (AG) agar plates (Sadowsky et al 1987). Nodule bacteria were purified by streaking onto the same medium.…”

Inactivation of the lpcC gene alters surface-related properties and symbiotic capability of Bradyrhizobium japonicum

“…Escherichia coli strains were grown aerobically at 37°C in Luria-Bertani (LB) medium. B. japonicum strains were grown aerobically at 30°C in AG medium (Sadowsky et al 1987). In the biofilm assay, B. japonicum strains were grown in Bergersen's minimal medium supplemented with 0Á4% (v/v) glycerol (BMM) (Bergersen 1961).…”