Film mulching reduces antibiotic resistance genes in the phyllosphere of lettuce

Phyllosphere is an important reservoir of antibiotic resistance genes (ARGs),but the transfer mechanism of ARGs from soil and air to phyllosphere remains unclear.This study demon-strated that soil-air-phyllosphere was the dominant ARG transfer pathway,and blocking it by film mulching can reduce typical phyllosphere ARGs in lettuce by 80.7％-98.7％ (89.5％ on average).To further eliminate phyllosphere ARGs in lettuce grown with film mulching,the internal soil-endosphere-phyllosphere transfer pathway deserves more attention.We ana-lyzed the ARG hosts and the resistome in lettuce rhizosphere and phyllosphere with film mulching via hybrid Illumina-Nanopore sequencing.Pseudomonas sp.7SR1 was more abun-dant than other ARG hosts,accounting for 1.0％ and 47.1％ of the total bacteria in rhizosphere and phyllosphere,respectively.The species has flagella that can promote mobility and can excrete extracellular polymeric substances and/or surfactant-like microbial products,which benefits its colonization in the phyllosphere.Impeding the migration of Pseudomonas sp.7SR1 via the soil-endosphere-phyllosphere pathway would be effective to further reduce ARGs in phyllosphere.Multidrug resistant genes were predominant in phyllosphere (40.3％of the total),and 87.6％ of the phyllosphere ARGs were located on chromosomes,indicat-ing relatively low horizontal gene transfer (HGT) potentials.This study provides insights into the transfer mechanism,hosts,and control strategies of phyllosphere ARGs in typical plants.