Interspecific rhizosphere interactions enhance secondary metabolite synthesis and volatile oil content in Atractylodes lancea through root exudates

Plant diversity often enhances ecosystem productivity, but the impact of interspecific interactions on secondary metabolism, which determines crop quality, is rarely reported. This study conducted a two-year field experiment on A. lancea [Atractylodes lancea (Thunb.) DC.]-maize (Zea mays L.) intercropping, including A. lancea monoculture (A), A. lancea and maize intercropping without separation (AI), with a permeable nylon root barrier (AN), or with an impermeable plastic root barrier (AP). Additionally, we recorded the volatile oil content (secondary metabolite of A. lancea), when its roots were treated with potential rhizosphere signals. The results showed that intercropping maize significantly increased the yield and volatile oil content of A. lancea, with the rhizome yield increasing by 52.2 %. The total content of four sesquiterpene volatile oils doubled, and the β-eudesmol and atractylodin contents increased by 1.3 times and 8.8 times, respectively. Notably, the potential rhizosphere signal—formononetin, isoliquiritigenin, and calycosin—significantly increased their contents in A. lancea. Furthermore, intercropping significantly increased the expression of key sesquiterpenoid synthesis genes (HMGS, HMGR, DXS, DXR, and FPS) in the rhizomes of A. lancea. The results indicate that root exudates from intercropped maize significantly enhance the expression of key enzyme genes for sesquiterpene synthesis in A. lancea, thereby increasing its volatile oil content. These findings will help further explore the mechanisms by which interspecific rhizosphere interactions promote crop quality and provide new insights into plant-plant interactions.