Effects of arbuscular mycorrhizal fungi on the bacterial community in strawberry roots

[Objective] Arbuscular mycorrhizal (AM) fungi can regulate rhizosphere microbial communities of plants, and alleviate continuous cropping obstacles. However, few studies have revealed the effects of AM fungi on the microbial community of continuously cropped strawberry. [Methods] A soil from a field that had been consecutively cultivated with strawberry for five cycles was used as the test substrate, and strawberry was used as the test plant in this pot experiment, and the effects of inoculating Funneliformis mosseae (FM) and Rhizophagus intraradices (RI) on the bacterial community in strawberry roots, respectively, were studied. [Results] The results showed that, compared with the control (CK), both FM and RI treatments increased the fresh and dry weights of strawberries and reduced the contents of available elements in the rhizosphere soils. The bacterial communities from the old roots' rhizosphere soils (OR), the new roots' rhizosphere soils (NR), and the new roots' endophytes (NE) all were analyzed, which showed that the OR bacterial communities had the highest number of genera. Both fungi reduced the richness of the NR bacterial communities, and the RI treatment also reduced its evenness. Compared with CK, the FM treatment significantly increased the relative abundance of Arthrobacter, and the RI treatment significantly increased the relative abundance of Lysobacter in the NR bacterial communities, and increased the relative abundance of Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium in the NE bacterial communities. Network structure analysis showed that both AM fungi decreased the density and the average degree of the networks, increased the positive correlation ratios between bacterial genera, and increased the modularity of the networks. The genus Ellin6067 was a keystone from both FM and RI treatments. Mantel analysis showed that this genus was significantly correlated with the plant total dry weight. [Conclusion] The study indicates that AM fungi tend to regulate the assembly of bacterial communities from newly grown roots, enrich functional microorganisms, and may synergistically promote strawberry growth, providing a development direction for green and sustainable production in strawberry.