Symbiotic nitrogen contribution and biodiversity of root-nodule bacteria nodulating Psoralea species in the Cape Fynbos, South Africa

► All eight Psoralea species had round-shaped, determinate type (desmodioid) nodules. ► Psoralea species obtain 60-88% of their N nutrition from symbiotic fixation. ► Psoralea species transport fixed-N as in the xylem stream. ► Microsymbionts varied in phenotypic characteristics, nodulation promiscuity, and N2-fixing efficacy. ► Psoralea species can associate with Rhizobium, Mesorhizobium and Burkholderia strains.