ENTEROBACTER-CLOACAE-A105, ISOLATED FROM THE SURFACE OF ROOT-NODULES OF ASTRAGALUS-SINICUS CV JAPAN, STIMULATES NODULATION BY RHIZOBIUM-HUAKUII BV RENGE

Several bacterial strains were isolated from the surface of root nodul es of Astragalus sinicus cv. Japan (known as renge-sou in Japanese), a green manure legume that grows in winter and which is used in rice fi elds to fertilize the soil in both Japan and China. These bacterial st rains stimulated the nodulation on renge-sou induced by strains of Rhi zobium huakuii bv. renge. From a taxonomic characterization of the iso lates, the strains were found to belong to the species Enterobacter cl oacae. It was found that strains of E. cloacae increased the number an d weight of nodules and the yield of the host plant when these strains were inoculated with a strain of R. huakuii bv. renge both in a test- tube nodulation assay and in soil from a rice field. E. cloacae influe nced nodulation at an appropriate ratio of cells of two bacterial stra ins. The timing of the inoculation of the two strains onto the host pl ant was also important. The effect of E. cloacae on the nodulation of renge-sou may be due to bacterial products such as exopolysaccharides.