Metagenomic sequencing reveals structural and functional differentiation of the rhizosphere bacterial communities associated with available potassium in Atractylodes lancea affected with root rot.

BACKGROUND: Atractylodes lancea is an economically valuable medicinal herb indigenous to China, and its yield and quality are severely threatened by root rot disease. The rhizosphere microenvironment plays a critical role in plant health. Yet, its relationship with root rot in A. lancea is poorly understood. METHODS: This gap was addressed by collecting rhizosphere soils from healthy A. lancea plants and those infected with root rot. The physicochemical properties of the soil were determined, and metagenomic sequencing was performed to determine differences in the diversity, structure, composition, and functional characteristics of the rhizosphere bacterial communities between the two groups. RESULTS: Compared with healthy plants, the contents of total nitrogen, total potassium, and available potassium in the rhizosphere soil of diseased plants increased significantly, by 8.11, 3.42, and 38.66%, respectively. Concurrently, the bacterial community diversity increased significantly, and the community structure exhibited an obvious separating trend between the two groups, with a marginally non-significant difference (P = 0.098). Pseudomonadota, Streptomyces, and Trinickia were relatively more abundant in the healthy group, while Acidobacteriota, Cyanobacteriota, Gemmatimonadota, Gemmatimonas, and Sphingomicrobium were significantly enriched in the diseased group according to independent samples Student's t-tests (P < 0.05). LEfSe analysis (LDA score > 4) revealed that all the differential genera in the healthy group belonged to the Burkholderiaceae family within Pseudomonadota. Functional prediction demonstrated that rhizosphere bacteria of healthy plants were predominantly enriched for genes involved in ABC transporter pathways, whereas diseased samples were enriched for secondary metabolite biosynthesis alongside significantly elevated abundance of auxiliary oxidoreductase genes. The abundance of auxiliary oxidoreductase genes was also significantly higher in the diseased group. Redundancy and correlation analyses showed that available potassium was strongly correlated with the divergence in the composition and function of the rhizosphere bacterial community. CONCLUSIONS: This study revealed that the occurrence of root rot was associated with imbalanced physicochemical properties of rhizosphere soil, shifts in bacterial community composition and structure, and alterations in metabolic functions of A. lancea. These findings elucidate rhizosphere responses linked to root rot and inform the sustainable cultivation of A. lancea.