Intraspecific Rice Intercropping Reduces the Rhizosphere Resistome in Association with Organic Acid and low-ARG-burden Microbiota Enrichment.

Antibiotic resistance genes (ARGs) in agricultural soils are an emerging environmental concern. However, sustainable strategies for reducing ARG in crop rhizospheres remain limited. Here, we investigated associations among rhizosphere metabolites, microbial communities, and ARG profiles in an intraspecific rice intercropping system. Compared with monoculture, intraspecific intercropping reduced the relative abundances of total ARGs and ARGs assigned to the Ranks I and II. Intercropping also altered rhizosphere metabolite profiles, with increased organic acid abundance, and was associated with convergent changes in microbial community composition. Nitrospirales, particularly Candidatus Sulfobium, was enriched under intercropping. MAGs assigned to this lineage contained relatively few annotated ARGs, which were predominantly classified as ARGs assigned to the Rank IV. Exogenous supplementation reproduced this field-associated pattern: citric acid treatment reduced total ARG and ARGs assigned to the Ranks I and II abundance and concurrently increased the relative abundance of Candidatus Sulfobium. These results support an association among rhizosphere organic acids, low-ARG-burden taxa, and reduced ARG abundance. Collectively, these findings highlight intraspecific rice intercropping as a low-input, source-control approach for cleaner rice production and ARG-risk mitigation.