Effects of Long-term Non-application of Phosphorus Fertilizer on Bacterial Community Structure and Metabolite Profiles of Sweetpotato Rhizosphere

Rhizosphere is the key part of belowground interaction between plant, microbes, and soil. Beneficial interactions between plant roots and rhizosphere microorganisms are pivotal for plant fitness. The aims of this study were to identify the response characteristics and their interactions of bacterial community structure and metabolites profiles in sweetpotato rhizosphere under long-term non-application of phosphorus (P) fertilizer. The research results can provide scientific basis for strengthening rhizosphere interactions and improving P utilization efficiency. Rhizosphere samples were collected from sweetpotato (Shangshu 19) grown in long-term (41 years) no fertilizer input (CK treatment), long-term application nitrogen (N) and potassium (K) fertilizers (NK treatment, as the long-term non-application of P fertilizer), and long-term application N, P, and K fertilizers (NPK treatment, as the long-term application of P fertilizer) soils. Then, soil bacterial community structure and metabolite profiles were analyzed by 16S rRNA high-throughput sequencing and liquid chromatography-mass spectrometry (LC-MS), respectively. Long-term non-application of P fertilizer significantly increased the relative abundances of Coprobacter, Cyclobacteriaceae, Pseudohongiella, Capnocytophaga, and Granulicatellain sweetpotato rhizosphere (P< 0.05). The cluster of orthologous groups of proteins (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the functions of these bacteria were mainly correlated to sugar metabolism and inositol phosphate metabolism. LC-MS analysis showed that long-term non-application of P fertilizer promoted the accumulation of lipid-like substances in sweetpotato rhizosphere, and galactose metabolism and phospholipase D signaling pathway were the top 2 differential metabolic pathways. There were significant negative correlations between bacteria with increased abundance with D-galactonate, mevalonate-P, and L-glutamate. Sweetpotato responds to low P stress through promoting sugar and inositol phosphate metabolism in the rhizosphere under long-term non-application of P fertilizer. This study linked the differential soil bacteria and metabolite profiles in the sweetpotato rhizosphere under long-term non-application of P fertilizer and provided new insights into plant–microbe interactions in soil.