Influence of Bradyrhizobium japonicum location and movement on nodulation and nitrogen fixation in soybeans

• Published in: Applied and Environmental Microbiology 1989-07, Vol.55 (7), p.1711-1716
• Main Authors: WADISIRISUK, P, DANSO, S. K. A, HARDARSON, G, BOWEN, G. D
• Format: Article
• Language: English
• Subjects: Bacteriology; Biological and medical sciences; fijacion del nitrogeno; fixation de l' azote; formation de nodosites; Fundamental and applied biological sciences. Psychology; Glycine max; inoculacion; inoculation; Microbiology; Microorganism-Plant Interactions; nitrogen fixation; nodulacion; nodulation; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; procesos de transporte en el suelo; racine; raices; rhizobium; root nodulation; roots; seed treatment; soil transport processes; traitement des semences; transport dans le sol; tratamiento de semillas
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.55.7.1711-1716.1989

The influence of seed and soil inoculation on bradyrhizobial migration, nodulation, and N2 fixation was examined by using two Bradyrhizobium japonicum strains of contrasting effectiveness in N2 fixation. Seed-inoculated strains formed fewer nodules on soybean (mosly restricted to the tap and crown roots within 0 to 5 cm from the stem base) than did bradyrhizobia distributed throughout the soil or inoculated at specific depths. Nodulation was greater below the depths at which bradyrhizobial cells were located rather than above, even though watering was done from below to minimize passive bradyrhizobial migration with percolating water. The most profuse nodulation occurred within approximately 5 cm below the point of placement and was generally negligible below 10 cm. These and other results suggest that bradyrhizobial migration from the initial point of placement was very limited. Nevertheless, the more competitive strain, effective strain THA 7, migrated into soil to a greater extent than the ineffective strain THA 1 did. Nitrogen fixation resulting from the dual-strain inoculations differed depending on the method of inoculation. For example, the amount of N2 fixed when both strains were slurried together onto the seed was about half that obtained from mixing the effective strain into the soil with the ineffective strain on the seed. The results indicate the importance of rhizobial distribution or movement into soil for nodulation, nodule distribution, strain competitiveness, and N2 fixation in soil-grown legumes.