Ecological studies of root-nodule bacteria introduced into field environments. 6. Antigenic and symbiotic stability in Lotononis rhizobia over a 12-year period

Diatloff, A.

Soil Biology and Biochemistry 99(2): 85-88


ISSN/ISBN: 0038-0717
DOI: 10.1016/0038-0717(77)90042-6
Accession: 000344888

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Rhizobia suited to Lotononis bainesii do not occur naturally in Australia. 2 serologically distinct strains of African origin were introduced into an isolated field station where perennial L. bainesii/Pangola grass pastures were grazed. Paddocks varied in the period of rhizobial occupancy from 5-12 years. Stability of 4 rhizobial characters: colony colour, effectiveness, cell antigens and antibiotic sensitivity were assessed from nodules on persisting L. bainesii. Both strains became established throughout the 782 ha. No changes were observed in colony colour or serological reaction. Symbiotically, 8.5% of isolates had a lower N-fixing capacity than stock cultures held in the laboratory although there were no ineffective isolates. Change in effectiveness was unrelated to serotype or to time of occupancy. There was also little change in antibiotic sensitivity although 1 isolate was tolerant to 15 ppm streptomycin. The red bacterium Protaminobacter rubra was recorded for the first time as a cohabitant of L. bainesii nodules. It was concluded that colony colour, serological and symbiotic properties were sufficiently stable to be of use in long-term ecological studies although antibiotic sensitivity appeared less stable.