Parasponia andersonii was nodulated by thirty four of thirty nine slow-growing rhizobia isolated from tropical legumes and by R. japonicum and JR. lupini. The nitrogenase activity of nodulated plants within a rhizobial treatment varied widely. Effective associations were obtained with some but not all isolates from Cajanus cajan, Centrosema pubescens, Crotalaria anagyroides, Flemingia congesta, Inocarpus fragiferum, Macroptilium lathyroides, Phaseolus calcaratus, Stizolobium deeringianum and Stylosanthes gracilis. Little or no nitrogen was fixed with rhizobia from Albizia stipulata, Cassia mimosoides, Desmodium microphyllum, Pterocarpus indicus, Uraria lagopoides, and the wide-host range cowpea Rhizobium strain CB 756. Fast-growing rhizobia from Leucaena leucocephala, Mimosa invisa, M. pudica, Sesbania grandiflora and Lablab pur-pur eus nodulated Parasponia with a low level of nitrogen fixation.
Isolates from Parasponia failed to nodulate most of the legumes usually nodulated by slow-growing rhizobia and when tropical legumes were nodulated, the association was either partially effective or ineffective; only isolate CP 283 was highly effective and promiscuous. Hosts normally nodulated with fast-growing rhizobia, including Leucaena and Mimosa were not nodulated with isolates from Parasponia.
It was concluded that the Parasponia-Rhizobium symbiosis is best located in the ‘cowpea miscellany’.