A Comparison of Rice Root Microbial Dynamics in Organic and Conventional Paddy Fields

The assembly of plant root microbiomes is a dynamic process. Understanding the roles of root-associated microbiomes in rice development requires dissecting their assembly throughout the rice life cycle under diverse environments and exploring correlations with soil properties and rice physiology. In this study, we performed amplicon sequencing targeting fungal ITS and the bacterial 16S rRNA gene to characterize and compare bacterial and fungal community dynamics of the rice root endosphere and soil in organic and conventional paddy fields. Our analysis revealed that root microbial diversity and composition was significantly influenced by agricultural practices and rice developmental stages (<i>p</i> < 0.05). The root microbiome in the organic paddy field showed greater temporal variability, with typical methane-oxidizing bacteria accumulating during the tillering stage and the amount of symbiotic nitrogen-fixing bacteria increasing dramatically at the early ripening stage. Redundancy analysis identified ammonium nitrogen, iron, and soil organic matter as key drivers of microbial composition. Furthermore, correlation analysis between developmental stage-enriched bacterial biomarkers in rice roots and leaf mineral nutrients showed that highly mobile macronutrient concentrations positively correlated with early-stage biomarkers and negatively correlated with later-stage biomarkers in both paddy fields. Notably, later-stage biomarkers in the conventional paddy field tended to show stronger correlations with low-mobility nutrients. These findings suggest potential strategies for optimizing microbiome management to enhance productivity and sustainability.