Serogroups of Rhizobium japonicum in Soybean Nodules as Affected by Soil Types
1967
Damirgi, S. M. | Frederick, L. R. | Anderson, I. C.
Employing a rapid agglutination test, serogroups of Rhizobium japonicum were distinguished by using homogenized nodule suspensions as antigens. Most of the nodules obtained from soybeans on Iowa soils were in one of four serogroups: 123, 135,. 31, and 3. Serogroup 123 was dominant, averaging 52% in all soils except a few highly alkaline soils dominated by 135. Serogroups 3 and 31 were found in small percentages in many soils. Serogroups 71a, 110, and 117 were rarely found. Generally, variability between soil sites on the same soil type was less than variability between soil types. Serogroup 123 occupied from 79 to 100% of the nodules in 4 soybean fields on Webster, and was present in about 40% of the nodules from Clarion, Winterset, Shelby, and Lagonda soils. In a soil toposequence grading from Clarion (pH 5.9) to Harpster (pH 8.3), 80% of the nodules from Clarion were serogroup 123, but 92% of the nodules from Harpster contained serogroup 135. The predominance of serogroup 123 or 135 seemed related to soil pH. In sterile soil, serotype 123 grew well at pH values from 6.1 to 8.2; in liquid culture, it had a lower pH limit of about 4.0. In sterile soil, growth of serotype 135 appeared best around pH 8.2; in liquid culture, it had a lower pH limit of 5.5. Cropping with soybeans appeared to increase the percentage of 123, but soil type had a greater influence on the distribution of serogroups than did previous cropping history. The factors which affect the dominance of a serogroup in soybean nodules need further evaluation.
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