Selecting Rhizobium meliloti for Inoculation of Alfalfa Planted in Acid Soils1
- Henry S. Lowendorf and
- Martin Alexander2
A study was conducted to obtain Rhizobium meliloti strains suitable for use with alfalfa grown in acid soils. Thirteen strains of R. meliloti were examined for their ability to grow in acidified culture medium, and seven of these were characterized for the ability to survive in acid and limed nonsterile soils or grow in the presence of the host legume, Medicago sativa L. The pH values of the most acid, defined medium that permitted growth of the bacteria from a small inoculum ranged from pH 5.3 to 6.0. For R. meliloti 411SE1 and GH1-1SE1, the minimum pH that allowed for growth, the critical pH, was not a dependable indicator of survival in a more acid medium. Strains of R. meliloti with relatively low critical pH values survived better in a limed soil but not in acid soils than strains with higher critical pH values. Three strains of R. meliloti previously identified as good inoculants for alfalfa in acid soils did not consistently survive better than other strains in a planted or unplanted acid soil of pH 5.3. However, the plants increased the population densities of these three strains more than other strains. These results suggest that R. meliloti strains suitable for inoculation of alfalfa in acid soils may be selected not by simple saprophytic properties but by their stimulation by the host legume in acid soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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