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Background and aims: The South African herbaceous legume species Lessertia capitata, L. diffusa, L. excisa L. incana and L. herbacea were introduced to Australia to assess plant establishment and survival, as well as the saprophytic ability of their root nodule bacteria (RNB). Methods: Five Lessertia spp., were inoculated with selected RNB strains and were sown in five different agroclimatic areas of the Western Australian wheat-belt during 2007 and 2008. Plant population and summer survival were evaluated in situ . Soil samples and nodules from host plants were also taken from each site. The re-isolated rhizobia were RPO1-PCR fingerprinted and their partial dnaK and nodA genes were sequenced to confirm their identity. Results: Plants achieved only poor establishment followed by weak summer survival. More than 83 % of the rhizobia re-isolated from Lessertia did not correlate with the original inoculants' fingerprints, and were identified as Rhizobium leguminosarum. The nodA sequences of the naturalised strains were also clustered with R. leguminosarum sequences, thus eliminating the likelihood of lateral gene transference from Mesorhizobium and suggesting a competition problem with indigenous rhizobia. Conclusion: The stressful soil conditions and high numbers of resident R. leguminosarum strains in Western Australian soils, and their ability to rapidly nodulate Lessertia spp. but not fix nitrogen are likely to preclude the adoption of Lessertia as an agricultural legume in this region. [ABSTRACT FROM AUTHOR]

Bradyrhizobium are N 2 -fixing microsymbionts of legumes with relevant applications in agricultural sustainability, and we investigated the phylogenetic relationships of conserved and symbiotic genes of 21 bradyrhizobial strains. The study included strains from Western Australia (WA), isolated from nodules of Glycine spp. the country is one genetic center for the genus and from nodules of other indigenous legumes grown in WA, and strains isolated from forage Glycine sp. grown in South Africa. The 16S rRNA phylogeny divided the strains in two superclades, of B. japonicum and B. elkanii , but with low discrimination among the species. The multilocus sequence analysis (MLSA) with four protein-coding housekeeping genes (dnaK , glnII , gyrB and recA) pointed out seven groups as putative new species, two within the B. japonicum , and five within the B. elkanii superclades. The remaining eleven strains showed higher similarity with six species, B. lupini , B. liaoningense , B. yuanmingense , B. subterraneum , B. brasilense and B. retamae. Phylogenetic analysis of the nodC symbiotic gene clustered 13 strains in three different symbiovars (sv. vignae, sv. genistearum and sv. retamae), while seven others might compose new symbiovars. The genetic profiles of the strains evaluated by BOX-PCR revealed high intra- and interspecific diversity. The results point out the high level of diversity still to be explored within the Bradyrhizobium genus, and further studies might confirm new species and symbiovars. [ABSTRACT FROM AUTHOR]