Effects of arbuscular mycorrhizal fungi on the bacterial communities of three compartments in strawberry roots

BACKGROUND: Arbuscular mycorrhizal (AM) fungi can regulate microbial communities in rhizosphere soil and promote plant growth. However, few studies have examined the regulated differences in microbial communities between new and old roots. A pot experiment was performed to study the effects of inoculation with Funneliformis mosseae (FM) and Rhizophagus intraradices (RI) on bacterial communities associated with new and old strawberry roots. RESULTS: Compared with the non-inoculation control (CK), both FM and RI treatments increased the fresh and dry weights of strawberry plants and decreased the soil available nutrition. Bacterial communities were analyzed in old root rhizosphere (ORR), new root rhizosphere (NRR), and new root endosphere (NRE). Among these, ORR had the highest number of bacterial genera. Both fungal inoculations reduced the richness of NRR bacterial communities, while RI treatment additionally reduced community evenness. Compared with CK, FM treatment significantly increased the relative abundance of Arthrobacter, whereas RI treatment significantly increased the relative abundance of Lysobacter in NRR communities, and of Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium in NRE communities. Overall, AM affected bacterial recruitment and assembly rather than changing the original community. Network structure analysis showed that both AM fungi decreased network density and average degree, increased the positive correlation ratios among bacterial genera, and enhanced network modularity. The genus Ellin6067 served as a keystone in both FM and RI treatments. Correlation analysis further showed that this genus was significantly correlated with total plant dry weight. CONCLUSIONS: These findings suggest that AM fungi tend to regulate the assembly of bacterial communities associated with new growth roots and enrich functional bacteria that may synergistically promote plant growth. Thus, this study provides additional evidence to the development direction for green and sustainable production in strawberry.