Diversity of endophytic bacteria of Dendrobium officinale under different growth conditions and screening of active strains

Objective  To compare and analyze the distribution characteristics of endophytic bacteria in wild and cultivated Dendrobium officinale, and screen active strains with strong colonization ability. To lay the foundation for improving the domestication of wild D. officinale and the quality of medicinal materials.

Method  The endophytic bacteria were isolated from the root, stem, leaf of D. officinale by tissue block separation method, and 16S rDNA sequence and phylogenetic tree were used to identify the isolated strains. The probioticactive bacterial strains with the abilities of phosphate-solubilizing, potassium-dissolving, nitrogen-fixing, siderophore-synthesizing, IAA-producting and antagonistic activity of pathogen were screened in vitro. The colonization dynamics of endophytic bacteria in tissue culture seedlings were observed after backgrafting and separation.

Result  A total of 285 endophytic bacteria strains were isolated from D. officinale, among which 217 were isolated from wild D. officinale, which were classified into three phylums and nine genera. Bacillus and Acinetobacter strains accounted for 79.26% and 8.76% of the total isolated strains respectively, and were the dominant bacteria. Only 68 endophytic bacteria strains were isolated from the cultivated D.officinale, which were classified into one phylum three genera, Burkholderia and Escherichia accounted for 54.41% and 30.88% of the total isolated strains respectively, and were the dominant bacteria. Only Pantoea was distributed in both wild and cultivated D. officinale. The number of endophytic species (9) and diversity index (0.85) of wild D. officinale were obviously higher than those of cultivated D. officinale (3 and 0.61 respectively). A total of 38 strains were obtained by active screening, accounting for 45% of the screened strains and three of four strains of endophytic bacteria from wild D. officinale showed good colonization in artificial tissue culture seedlings.

Conclusion  The biodiversity and community structure of endophytic bacteria of wild and artificially cultivated D. officinale are obviously different and the endophytic bacteria contains abundant potential of growth promotion.