Objective: Genetic diversity of the rhizobial bacteria nodulating Tibetia himalaica in the eastern part of Qinghai-Tibet Plateau (Ganzi State, Sichuan) were evaluated.
Methods: The pure culture method was used for isolating the rhiobial strains from the nodules. BOXAIR, 16S rDNA sequences, 16S rDNA PCR-RFLP and Principal Component Analysis (PCA) were used to determine the genetic diversity and phylogenetic relationships. The growth in different salt contents, pH and temperatures were tested.
Results: In total 22 strains were isolated from 12 samples in 8 counties. The strains tested were classified into 4 clusters in 16S rDNA PCR-RFLP, and 8 clusters were formed in BOXAIR. The 16S rDNA Simpson genetic diversity index was D = 0. 872. The strains tested were closely related to Rhizobium (11/22 strains), Mesorhizobium (4/22 strains) and Rhizobium- Agrobacterium (7/22 strains). All strains could regularly grow in YMA medium amended with 1% NaCl, and 15/22 strains could grow in 4% NaCl. SCAU679, SCAU694 and SCAU706 could adapt to 7% NaCl, while SCAU689 could tolerant 8% NaCl. Among the strains tested, 15 strains could grow in the pH range from 4.0 to 11; 16 isolates grew well from 4 to 45 degrees C, and all of 22 strains could grow at 28 degrees C after treatment at 60 degrees C for 10 min.
Conclusion: This study revealed the high genetic diversity of the rhizobia isolated from Tibetia himalaica in the eastern part of Qinghai-Tibet Plateau. The strains tested were adapted to high salt, different range of temperatures and pH.