Genetic diversity of rhizobial bacteria nodulating Tibetia Himalaica in eastern Qinghai-Tibet plateau

Abstract:

Abstract:［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，SCAU694and 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℃，and all of 22 strains could grow at 28 ℃ after treatment at 60℃ 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．

Key words:Keywords: Qinghai-Tibet plateau，Tibetia himalaica，rhizobial，genetic diversity，PCA (Principal component analysis)，phylogeny