Ecological studies of root nodule bacteria introduced into field environments part 6 antigenic and symbiotic stability in lotononis rhizobia over a 12 year period

Diatloff, A.

Soil Biology and Biochemistry 9(2): 85-88


ISSN/ISBN: 0038-0717
Accession: 005210754

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Rhizobia suited to L. bainesii do not occur naturally in Australia. Two serologically distinct strains of African origin were introduced into an isolated field station where perennial Lotononis-pangola grass pastures were grazed. Paddocks varied in the period of rhizobial occupancy from 5-12 yr. Stability of 4 rhizobial characters: colony color, effectiveness, cell antigens and antibiotic sensitivity, were assessed from nodules on persisting Lotononis. Both strains became established throughout the 782 ha. No changes were observed in colony color 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. Changes 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 parts/106 streptomycin. The red bacterium Protaminobacter rubra was recorded for the first time as a cohabitant of Lotononis nodules. Colony color, serological and symbiotic properties are sufficiently stable to be of use in long-term ecological studies although antibiotic sensitivity appears less stable.