The antimicrobial action of apigenin against Phytophthora sojae and its recruitment effect on biocontrol agents in soybean rhizosphere

BACKGROUND: Plants release many kinds of metabolites in the rhizosphere, which recruit both pathogenic agents and beneficial microbes (improve plant growth or resist pathogens). Phytophthora sojae is a notorious plant pathogenic oomycete which causes the destructive Phytophthora root and stem rot (PRR) of soybean. However, it is not clear which beneficial biogenic metabolites are released from the resistant soybean that recruit beneficial microbes to defend Phytophthora sojae. We compared the rhizosphere components of a pair of soybean near-isogenic lines the susceptible Williams (W) and the resistant Williams82 (W82) pre-inoculation and post-inoculation with Phytophthora sojae, and analyzed the impact of the pathogen on plant rhizosphere composition. It is expected to screen the beneficial metabolites and microbes controlling PRR from the differential components of the resistant soybeans. RESULTS: Rhizosphere soil of W82 and W post Phytophthora sojae inoculation had stronger inhibition effects on Phytophthora sojae infection to soybean than that of W82 and W. But there was no significant difference in α-diversity of rhizosphere microbiome between soybean pre-inoculation and post-inoculation. Some specialists in W82 rhizosphere induced by Phytophthora sojae, such as metabolites apigenin, and microbes Bacillus sporothermodurans had great inhibition effects on PRR. PRR incidence of apigenin treatment (41.3%) and Bacillus sporothermodurans (48%) treatment were significantly lower than control (equal volume of sterilized water with LB medium) (53-54%). Apigenin had the strongest inhibition effect on the mycelial growth of Phytophthora sojae among these metabolites and it was extremely related to the microbiome construction and the population of Bacillus in the rhizosphere. CONCLUSION: Apigenin in the rhizosphere inhibits Phytophthora sojae directly and participates in the microbiome assembling in the rhizosphere and mediating the recruitment of Bacillus sporothermodurans to help soybean to resist PRR. © 2025 Society of Chemical Industry.