Reductive soil disinfestation mitigates antibiotic resistance gene risk in the soil-lettuce continuum by...

Reductive soil disinfestation (RSD) and chemical fumigation serve as effective methods for controlling soil-borne pathogens, yet their effects on soil antibiotic resistome remain poorly understood. This study combined high-throughput qPCR (HT-qPCR) and metagenomic sequencing to evaluate the impacts of dazomet fumigation (DZ) and RSD amended with alfalfa (AL) and molasses (MO) on antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and bacterial communities in an ARG-contaminated soil. Results demonstrated that both DZ and RSD treatments significantly altered the soil resistome and bacterial community. HT-qPCR revealed that DZ significantly increased the relative abundance of total ARGs, MGEs and high-risk ARGs (Rank I and Rank II) by 86.59 %, 43.12 %, 36.81 %, and 40.88 %, respectively, while RSD treatments effectively reduced MGEs by 53.96-63.30 % and significantly suppressed Rank II high-risk ARGs. Metagenomic sequencing further indicated that RSD, particularly AL, outperformed DZ in reducing most ARGs classes, with pronounced effects on predominant ARGs such as macB (16.32 %), tetA(58) (24.14 %), and TxR (29.31 %). Correlation analyses suggested that RSD mitigates ARGs contamination by modulating the dominant bacterial community, especially suppressing ARG hosts while enriching antagonists, and improving soil physicochemical properties. Variance partitioning analysis attributed greater explanatory power to bacterial community than to physicochemical properties in shaping high-risk (18.44 % vs. 3.72 %) and high-abundance (11.90 % vs. 2.79 %) ARG profiles. Moreover, RSD considerably reduced the ARGs transmission risk from soil to lettuce. These findings establish RSD as an effective strategy to curb ARGs dissemination in soil-plant system and support its adoption for safer agricultural production.