Characterisation of rhizobia nodulating Galega officinalis (goat's rue) and Hedysarum coronarium (sulla)

Many legumes can colonise low nitrogen (N) soils due to their ability to fix atmospheric N2 via symbiotic bacteria in root nodules. Galega officinalis and Hedysarum coronarium are legumes that have naturalised and become common weeds in New Zealand. Previous work outside of New Zealand indicated that they only form effective nodules with their respective symbionts, Rhizobium galegae and R. sullae. Here, analysis of 16S rRNA and housekeeping genes, and plant nodulation tests were carried out on five selected bacterial strains isolated from root nodules of both legumes sampled at one site each. Only Rhizobium galegae strains were isolated from G. officinalis and selected strains induced effective nodules when re-inoculated onto the host plant. Agrobacterium vitis, R. galegae and R. sullae strains were isolated from nodules of H. coronarium, but only R. sullae induced effective nodules on this plant. Results agree with previous reports that these legume species are highly specific in the rhizobia they form effective nodules with, but further work is required to confirm this. © 2012 New Zealand Plant Protection Society (Inc.)