Manure Application Did Not Enrich Antibiotic Resistance Genes in Root Endophytic Bacterial Microbiota of Cherry Radish Plants
Authors: Ji-Zheng He
Hui Yan
Qing-Lin Chen
Deli Chen
Yu-Jing Zhang
Hang-Wei Hu
Jun-Tao Wang
Journal: Applied and Environmental Microbiology (2020)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: antibiotic resistance genes; endophyte; phyllosphere; plant microbiome; resistome.
Affiliations: Faculty of Veterinary and Agricultural Science, The University of Melbourne, Parkville, Victoria, Australia, College of Animal Science and Technology, Agricultural University of Hebei, Baoding, China, Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia

Abstract:  Growing evidence suggests that livestock manure used as organic fertilizer in agriculture may lead to the potential propagation of antibiotic resistance genes (ARGs) from "farm to fork." However, little is known about the impacts of manure fertilization on the incidence of ARGs in the plant-associated microbiomes (including rhizosphere, endosphere, and phyllosphere), which hampers our ability to assess the dissemination of antibiotic resistance in the soil-plant system. Here, we constructed a pot experiment to explore the effects of poultry and cattle manure applications on the shifts in the resistome in the plant microbiome of harvested cherry radish. A total of 144 ARGs conferring resistance to eight major classes of antibiotics were detected among all the samples. Rhizosphere and phyllosphere microbiomes harbored significantly higher diversity and abundance of ARGs than did root endophytic microbiomes of cherry radish. Manure application significantly increased the abundance of ARGs in the rhizosphere and phyllosphere but not in the endophytes of the root, which is the edible part of cherry radish. Soil and plant microbiomes changed dramatically after manure applications and clustered separately according to different sample types and treatments. Structural equation modeling revealed that bacterial abundance was the most important factor modulating the distribution patterns of soil and plant resistomes after accounting for multiple drivers. Taken together, we provide evidence that enrichment of the resistome in the rhizosphere and phyllosphere of cherry radish is more obvious than with the endosphere after manure application, suggesting that manure amendment might not enhance the dissemination of ARGs into the root of vegetables in the pot experiment.IMPORTANCE Our study provides important evidence that manure application increased the occurrence of ARGs in the rhizosphere and phyllosphere of cherry radish, compared with that in the endophytic bacterial microbiota of root, which is the edible part of cherry radish. Our findings suggest that although manure amendment is a significant route of ARGs entering agricultural soils, these manure-derived ARGs may be at low risk of migrating into the endophytes of root vegetables. 

Retracted: No

PubPeer comments:
 Dear Authors, Please, have a closer look at your Figure 4 in the article. The caption says it is about classes of bacteria, but then classes are only for poultry manure, whereas for the cattle manure treatment the graph gives bactarial phyla. Thus it it impossible to compare treatment and to figure relative changes at different taxonomic levels. Would be nice if you can correct this Figure. I use the pubpeers plantform, rather than personal communication, because the comments here can be seen by other readers, whereas personal communication cannot, and, sadly, authors oftern resort to neglect the questionscomments sent via personal e-mail. Hope to see your response here! ,