GENETIC-RELATIONSHIPS AMONG RHIZOPINE-PRODUCING RHIZOBIUM STRAINS

Chromosomal and symbiosis-related genotypes of rhizopine-producing and non-producing isolates of Rhizobium meliloti and Rhizobium leguminosa rum were examined by multilocus enzyme electrophoresis and RFLP. The d istribution of rhizopine production in both species was found to be in dependent of host genotype, Conversely, rhizopine production was assoc iated with particular symbiotic plasmid types, this association may ex plain the observed distribution of rhizopine production in R. legumino sarum and R. meliloti. Rhizopine synthesis (mos) genes showed greater sequence divergence than rhizopine catabolism (moc) genes in both R. m eliloti and R. leguminosarum. Furthermore, mos and moc genes were less divergent in R. leguminosarum than R. meliloti, suggesting a more rec ent evolution in the former species.