Diversity of bacterial endophytes in Panax ginseng and their protective effects against pathogens.

Although endophytic bacteria are known to colonize Panax ginseng, little is known about their diversity and roles. We addressed in the present study by comparing endophytic bacterial populations in P. ginseng plants of different ages (2-6 years) and in various tissue types (root, stem, leaf, and flower stalk). A total of 116 strains assigned to 42 species were identified by 16S rDNA sequencing. The predominant phylum was Firmicutes. Two-year-old ginseng plants and root tissues showed the greatest diversity of endophytic bacteria, with Bacillales being the predominant order. The antifungal activity of isolates against two pathogens, Cylindrocarpon destructans and/or Botrytis cinerea, was evaluated in dual-culture assays. In total, 28 strains showed antifungal activity with PgBE14 (Bacillus amyloliquefaciens), PgBE40 (B. megaterium), PgBE39, PgBE45 (Pseudomonas frederiksbergensis), and PgBE42 (Staphylococcus saprophyticus) inhibiting both pathogens. These results improve our understanding of the structure and diversity of endophytic bacterial communities of P. ginseng and identify strains with antifungal activity that have potential applications as biocontrol agents.