Plant Host Provenances Affect Taxonomic Composition of Root-Associated Culturable Bacteria from Tripterygium wilfordii Hook f. and Their Plant Growth Promoting Properties

Plant-associated microbes play a crucial role in host growth, health, and stress resistance. Host plants significantly influence the assembly of their microbial communities. To examine the influence of plant provenance on bacterial composition and plant growth promoting (PGP) properties, we compared readily culturable bacteria isolated from the root interior and rhizosphere of Tripterygium wilfordii Hook f., a woody Chinese medicinal plant, across three provenances grown in different regions. Regardless of the host growing environment, the abundance of endophytic bacterial colonies followed the trend: Fujian provenances > Hunan provenances > Hubei provenances. A total of 227 isolates were classified into 21 genera from the root interior and 40 genera from the rhizosphere, with Pseudomonas and/or Bacillus as the dominant genera. The taxonomic composition varied across plant provenances and host growing environments. Plants from the same provenance but cultivated in different locations exhibited greater similarity in their endophytic bacterial composition. The majority of the assayed strains displayed one or more PGP traits. Local plants harbored a higher proportion of PGP strains than non-local plants. Our findings indicate that plant provenance significantly influences the composition of root-associated culturable bacteria, particularly endophytic communities. Plants in their native environments may recruit PGP bacteria to enhance their fitness.