The effects of species diversity and co-inoculation with plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi on the Chinese medicinal plant Codonopsis pilosula "Ludangshen"

"Ludangshen" (Codonopsis pilosula), a medicinal material from Changzhi City, Shanxi Province, China is used extensively in traditional Chinese medicinal practice. Arbuscular mycorrhizal fungi (AMF) are known to promote the growth and development of medicinal plants and enhance the accumulation of their secondary metabolites. The purpose of this study was to clarify the important effects of AMF on the medicinal components and cultivation yield of C. pilosula by investigating the AMF diversity in wild C. pilosula and carry out inoculation tests using AMF and plant growth-promoting rhizobacteria (PGPR) in the laboratory. The results showed that AMF colonization ratios ranged from 65.33 % to 83.33 %. Seven genera and 32 species of AMF were identified using morphological methods. The dominant genera were Glomus and Acaulospora, with Glomus versiforme being the dominant species. Fifteen genera were detected using high-throughput sequencing, confirming that Glomus was the dominant genus. The Glomus species represented the biotic factors, while available phosphorus and urease were the abiotic factors that most affected the medicinal effectiveness of "Pingshun ludangshen". The coapplication of AMF and PGPR increased plant height and leaf area, and significantly elevated the contents of lobetyolin and atractylenolide III (the two medicinal factors) in C. pilosula. The top-down carbon flow and bottom-up nutrient flow contribute to the establishment of metabolic networks among C. pilosula, AMF, and PGPR. AMF provides an effective solution to the common challenges of low active ingredient content and poor yield faced in the artificial cultivation of medicinal plants by forming a symbiotic relationship with PGPR.