Native bradyrhizobia from Los Tuxtlas in Mexico are symbionts of Phaseolus lunatus (Lima bean)

Los Tuxtlas is the northernmost rain forest in North America and is rich in Bradyrhizobium with an unprecedented number of novel lineages. ITS sequence analysis of legumes in polycultures from Los Tuxtlas led to the identification of Phaseolus lunatus and Vigna unguiculata in addition to Phaseolus vulgaris as legumes associated with maize in crops. Bacterial diversity of isolates from nitrogen-fixing nodules of P. lunatus and V. unguiculata was revealed using ERIC-PCR and PCR-RFLP of rpoB genes, and sequencing of recA, nodZ and nifH genes. P. lunatus and V. unguiculata nodule bacteria corresponded to bradyrhizobia closely related to certain native bradyrhizobia from the Los Tuxtlas forest and novel groups were found. This is the first report of nodule bacteria from P. lunatus in its Mesoamerican site of origin and domestication.