The Cd-Tolerance of Pepper ( Capsicum annuum L.) Is Linked with the Rhizosphere Bacterial Community Composition and Rhizosphere Soil Metabolite Profiles

Cadmium (Cd) poses a serious threat to plant growth, so the selection and breeding of Cd-tolerant pepper cultivars are effective methods to reduce Cd hazards. This study identified C. annuum G03 as a Cd-tolerant cultivar, evidenced by its superior leaf physiological activity under Cd stress compared to the sensitive C. annuum C07. 16S rDNA sequencing revealed a more complex bacterial symbiotic network in the bulk soil, rhizosphere, and root endophyte of C. annuum G03, enhancing its buffering capacity against Cd stress. Furthermore, correlation analysis between rhizosphere bacteria and metabolites indicated that Armatimonadota and Bdellovibrionota were the key functional bacteria of C. annuum G03. They can influence the levels of key metabolites such as nerolidol, glutathionylspermine, and alpha-linolenic acid, thereby reducing antioxidant damage and Cd ion uptake in plant roots. These findings provide valuable insights into the microbial mechanisms underpinning the tolerance of pepper to Cd stress.