Infectivity and Competitive Ability of Fast and Slow Growing Rhizobium Strains on Soybeans

Abstract

Three Rhizobium strains including two fast-growers 440 and Mar 1 and one slow-grower 110 were used singularly and in combination of two to inoculate two soybean varieties, namely Palmetto and Kahala. The Rhizobium strains were indentifiable with antibiotic markers. The experiment was conducted in both the Leonard Jar and in the field where soybeans had been cultivated for many years. In the Leonard Jar experiment, all Rhizobium treatments performed significantly better than the control in nodule formation and plant dry mass production. For field trial, no significant Rhizobium effects were observed. In general, Kahala was more responsive to Rhizobium inoculation than Palmetto. The isolation tests indicated that the probality of recovering the original inoculated strains in nodules was high. However, some strains were more competitive than the others. Mar 1 failed to be recovered in competition with strain 440 or with indigeneous strains in the soil. On the other hand, strains 440 and 110 could be recovered successfully in all cases.