Nodulation studies on legumes exotic to Australia: Hedysarum coronarium

Symbiotic experiments in glasshouse, controlled environment cabinet, and field were conducted with four lines of sulla (Hedysarum coronarium) and 15 strains of Rhizobium spp. This plant is highly Rhizobium-specific and appropriate strains are most unlikely to occur naturally in Australia. Under several sets of experimental conditions, H. coronarium nodulated abundantly and effectively with homologous rhizobia introduced from Spain and Italy. The optimum temperature for nitrogen fixation was relatively low (approx. 21°C) but significant interactions between line of host, strain of rhizobia, and growth temperature were frequent. The rhizobia were persistent in soil.