Four strains of Rhizobium leguminosarum bv. trifolii were screened for their use in inoculants for red clover (Trifolium pratense) in the Soil Microbiology Sector, Department of Soils, University of Rio Grande do Sul, Porto Alegre, Brazil, from January 1994 to March 1995. In greenhouse experiments, all four strains presented similar efficiency in nitrogen fixation. However, when mixed strains were used, the strain SEMIA 222 was more effective in nodule formation. In a yeast manitol sucrose medium, growth rate was higher for strains SEMIA 222, T107 and T154, than for strain SEMIA 235. Generation time was lower for strain 222, followed by T107 and T154, and highest for 235. Strains 222 and T154 survived well in an inoculant with sterilized peat carrier evaluated at six months of storage, though the latter dominated the population in an inoculant with mixed strains. These two strains survived in a similar manner in inoculated seed.
Rhizobium leguminosarum bv; trifolii; selection of strains; Trifolium pratense