AMF inhibit the production of phenolic acid autotoxins at the seed-filling stage in soybeans with continuous monocropping

Abstract Background Soybean is the main oil crop in Northeast China. Continuous monocropping is more commonly used for soybean production due to rising market demand and arable land constraints. However, autotoxic substances, such as phenolic acids, produced by continuously cropped soybean can reduce yield and quality. The mycorrhiza formed of Arbuscular mycorrhizal fungi (AMF) and plant roots regulate the metabolic activities of the host plant and increase its disease resistance. The main purpose of this study was to inhibit the production of phenolic acids and determine the adverse effects on the growth of continuous monocropping soybean by inoculating Funneliformis mosseae (F. mosseae). Results Transcriptomics results showed that the production of phenolic acids in continuous monocropping soybean roots was mainly regulated by the expression of the CHS6, PCL1, SAMT, SRG1, and ACO1 genes, and the expression of these genes was significantly downregulated after inoculation with F. mosseae. Metabolomics results showed that continuous monocropping soybean roots inoculated with F. mosseae inhibited phenolic acid production through the phenylpropane biosynthetic, α-linoleic acid, linoleic acid, and other metabolic pathways. Phenolic acids in the phenylpropane metabolic pathway, such as 4-hydroxybenzoic acid, phthalic acid, and vanillic acid, decreased significantly after inoculation with F. mosseae. The combined analysis of the two showed that genes such as YLS9 and ARF3 were positively correlated with 4-hydroxybenzoic acid and so on, while genes such as CHS6 and SRG1 were negatively correlated with butyric acid and so on. Conclusion F. mosseae regulated the expression of functional genes and related phenolic acid metabolic pathways produced by continuous monocropping soybean roots, inhibiting the production of phenolic acid autotoxic substances in continuous cropped soybean, and slowing down the disturbance of continuous monocropping. This study provides a new solution for continuous monocropping of plants to overcome the autotoxicity barrier and provides a new basis for the development and utilization of AMF as a biological agent.