[Symbiotic efficiency and genetic diversity of the rhizobia isolated from Leucaena leucocephala in Liangshan Prefecture].

OBJECTIVE We analyzed the symbiotic efficiency and genetic diversity of rhizobia isolated from Leucaena leucocephala in Liangshan Prefecture of SichuanProvince. METHODS We studied genetic diversity of these isolates with 16S rRNA RFLP, BOX-PCR and AFLP fingerprinting, and constructed phylogenetic tree based on the concatenated sequences of the four housekeeping genes 16S rRNA, recA, atpD and glnII. The nodulation ability and the symbiotic efficiency of the isolates were tested by plant inoculation assay on their original host plant. RESULTS Genetic diversity and phylogenetic tree indicate that 26 isolates were assigned as Sinorhizobium, 3 Bradyrhizobium, 3 Rhizobium and 1 Mesorhizobium. SCAU203 might represent a new Rhizobium group, SCAU211 might represent a new Bradyrhizobium group, the other three representative strains were located in three phylogenic branches and closely related to S. americanum, M. plurifarium and R. huautlense, respectively. In the nodulation and symbiotic efficiency assay, only 2 of the 20 isolates promoted the growth of L. leucocephala, but 3 isolates had a growth slowing effect on the host, while the other isolates (84%) were ineffective on symbiotic nitrogen fixation. CONCLUSION The majority of rhizobia isolated from L. leucocephala in Liangshan Prefecture were ineffective on symbiotic nitrogen fixation.