Diversity of endophytic bacteria in different tissues of triploid Populus tomentosa

Abstract:

[Background] Triploid Populus tomentosa is suitable for the ecological and economic development of the Yellow River and serves as an important tree species for forestry extension projects in China. Endophytic bacteria of triploid P. tomentosa play a role in the disease prevention, growth promotion, nitrogen fixation, and biological repair. [Objective] The objective was to analyze the diversity of endophytic bacteria and fully explore the microbial resources in triploid P. tomentosa. [Methods] In this study, the diversity of endophytic bacterial community in the roots, stems and leaves of P. tomentosa from the research base of Beijing Forestry University in Guanxian county, Shandong province was analyzed via 16S rRNA gene high-throughput sequencing and plate streaking. The variation trends and rules of endophytic bacterial diversity in different tissues of triploid P. tomentosa were clarified to lay a theoretical foundation for the further application of endophytic bacteria. [Results] The endophytic bacteria of triploid P. tomentosa had the highest richness and diversity in the roots while the lowest in the leaves. Pseudomonas and Actinobacteria were the dominant phyla, and Burkholderia, Pseudonocardia, and Acidovorax were the dominant genera. The structure of endophytic bacterial community varied among different tissues. The functions of the endophytic bacteria mainly involved amino acid metabolism, vitamin metabolism, degradation of aromatic compounds, and glycolysis. A total of 217 endophytic bacterial strains were isolated, belonging to 44 species of 23 genera. Among them, four strains shared the 16S rRNA gene sequence similarity below 97.5%, which might be new taxa. [Conclusion] In conclusion, the diversity of endophytic bacteria in the roots, stems and leaves of triploid P. tomentosa was significant. The diversity and richness of endophytic bacteria were higher in the roots than in the stems than in the leaves. Some endophytic bacterial resources were obtained by traditional isolation and culture methods, including 4 strains with 16S rRNA gene sequence similarity less than 97.5%. However, the results of high-throughput sequencing showed that a large number of endophytic bacterial strains had not been cultured in this experiment. It was necessary to further develop new high-throughput isolation, culture and identification methods to fully explore more uncultured and difficult endophytic bacterial strains.

Key words:triploid Populus tomentosa;root;stem;leaf;endophytic bacteria;bacteria diversity