Evaluation location: California, United States
Medicago rigiduloides accessions were planted in sterile conditions and inoculated with a common rhizobium strain. Effective nodulation after 6-10 weeks was noted. If an accession nodulates (>0%) with this rhizobium it is not Medicago rigiduloides. The Australian at the South Australian Dept. of Agriculture have determined that the Medicago species rigidula and rigiduloides can be separated on the basis of rhizobium selectivity. For example, Medicago rigidula, the Western Mediterranean species, nodulates with a common Medic rhizobium that inoculates some 90% of annual medics, including M. polymorpha and even M. doliata. However, Medicago rigiduloides is very specific in its rhizobium requirement and will not nodulate with the common rhizobium strain as it does with other medic species. The South Australians have found a specific rhizobium strain from the Middle East that nodulates M. rigiduloides.