Ecological studies of root nodule bacteria introduced into field environments part 5 a critical examination of the stability of antigenic and streptomycin resistance markers for identification of strains of rhizobium trifolii

Brockwell, J.; Schwinghamer, E.A.; Gault, R.R.

Soil Biology and Biochemistry 9(1): 19-24


ISSN/ISBN: 0038-0717
DOI: 10.1016/0038-0717(77)90056-6
Accession: 005210753

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Marked strains of R. trifolii, distinguishable from other strains antigenically and by streptomycin resistance, were introduced by seed inoculation of subterranean clover (Trifolium subterraneum L.) into a field environment having a natural population of R. trifolii. Isolates from nodules obtained periodically during the following 41 mo. were classified using both methods of identification in parallel. This procedure made it possible to determine the reliability of each method independently. There was a gradual disappearance of the inoculum strains which occurred more rapidly in plots of cultivar 'Woogenellup' than in plots seeded with cultivar 'Mount Barker'. At 5 harvests, there was 95% (or greater) correspondence between inoculum survival using either method of identification. There was evidence that a small proportion of the progeny of the inocula sustained independent loss of antigenic character and/or streptomycin resistance in the field or, alternatively, that strains occurring naturally acquired these characteristics. A few nodules contained more than 1 strain of rhizobia. These exceptions occurred at low frequency and did not interfere substantially with identification results. It is concluded that gel immune diffusion serology and the use of streptomycin-resistant mutants are both reliable methods for identifying strains of rhizobia reisolated from field environments.