Modification of Rhizosphere Bacterial Community Structure and Functional Potentials to Control Pseudostellaria heterophylla Replant Disease

Replant disease caused by negative plant-soil feedback commonly occurs in a Pseudostellaria heterophylla monoculture regime. Here, barcoded pyrosequencing of 16S ribosomal DNA amplicons combined with phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis was applied to study the shifts in soil bacterial community structure and functional potentials in the rhizosphere of P. heterophylla under consecutive monoculture and different soil amendments (i.e., bio-organic fertilizer application [MF] and paddy-upland rotation [PR]). The results showed that the yield of tuberous roots decreased under P. heterophylla consecutive monoculture and then increased after MF and PR treatments, which was consistent with the changes in soil bacterial diversity. Both principal coordinate analysis and the unweighted pair-group method with arithmetic means cluster analysis showed the distinct difference in bacterial community structure between the consecutively monocultured soil (relatively unhealthy soil) and other relatively healthy soils (i.e., newly planted soil, MF, and PR). Furthermore, taxonomic analysis showed that consecutive monoculture of P. heterophylla significantly decreased the relative abundances of the families Burkholderiaceae and Acidobacteriaceae (subgroup 1), whereas it increased the population density of families Xanthomonadaceae, Phyllobacteriaceae, Sphingobacteriaceae, and Alcaligenaceae, and Fusarium oxysporum. In contrast, the MF and PR treatments recovered the soil microbiome and decreased F. oxysporum abundance through the different ways; for example, the introduction of beneficial microorganisms (in MF) or the switching between anaerobic and aerobic conditions (in PR). In addition, PICRUSt analysis revealed the higher abundances of membrane transport, cell motility, and DNA repair in the consecutively monocultured soil, which might contribute to the root colonization and survival for certain bacterial pathogens under monoculture. These findings highlight the close association between replant disease of P. heterophylla and the variations in structure and potential functions of rhizosphere bacterial community.