Simulated Leaching of Foliar Applied Copper Bactericides on the Soil Microbiome Utilizing Various Beta Diversity Resemblance Measurements

Authors: STRAYER-SCHERER, AMANDA - Auburn University; TIMILSINA, SUJAN - University Of Florida; LIAO, YING-YU - University Of Florida; YOUNG, MIKAEEL - University Of Central Florida; Rosskopf, Erin; VALLAD, GARY - University Of Florida; SANTRA, SWADESHMUKUL - University Of Florida; JONES, JEFFREY - University Of Florida; Hong, Jason; PARET, MATHEWS - University Of Florida

Submitted to: Microbiology Spectrum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2022
Publication Date: 5/10/2022
Citation: Strayer-Scherer, A., Timilsina, S., Liao, Y., Young, M., Rosskopf, E.N., Vallad, G.E., Santra, S., Jones, J.B., Hong, J.C., Paret, M. 2022. Simulated Leaching of Foliar Applied Copper Bactericides on the Soil Microbiome Utilizing Various Beta Diversity Resemblance Measurements. Microbiology Spectrum. Article e01481-21.
DOI: https://doi.org/10.1128/spectrum.01481-21

Interpretive Summary: Plants can be infected by bacterial pathogens, which can stunt growth, limit yield, and cause crop loss. Growers have depended upon copper materials to manage these pathogenic bacteria. However some of these microorganisms have become resistant to copper, leaving growers with fewer options to manage these pathogens. Therefore, researchers are investigating ways to manipulate the copper so that it can overcome resistance. Nanomaterials, products whose single product size is between 1-100 nanometers, can exhibit novel characteristics at that scale. Nano-copper was found to be lethal to these pathogenic bacteria and their copper-resistant counterparts. One concern associated with application of nanoparticle pesticides is whether they affect the total soil bacterial population. The soil bacterial community is very important for plant health, as the microbiome provides nutrients and offers protection from soil pathogens. From this study it was discovered that copper and one of the tested nanomaterials effected the soil bacteria, however the diluted nanomaterial had the same effect on the microbiome as adding water to the soil. If the nanomaterial were to drip into the soil, it likely that it would be sufficiently diluted to not impact the soil microbiome. Thus, this research provides growers with another tool for controlling bacteria pathogens that has limited impact on the environment.

Technical Abstract: Copper bactericides are routinely used to control Xanthomonas perforans (XP), causal agent of bacterial spot of tomato. Given the widespread tolerance to copper in XP strains in FL, USA, nanotechnology-based elemental composites have gained interest for their potential applications in agriculture in part due to their enhanced antimicrobial properties and toxicity to copper-tolerant strains. However, little is known about the potential impact of conventional copper bactericides as well as nano-based elemental composites on soil microbial communities, as determined by high-throughput sequencing of the 16S ribosomal deoxyribonucleic acid. We compared the effects of 2 and 200'µg/mL of core-shell (CS), a metallic copper composite, and a conventional copper bactericide + mancozeb (Cu+Man) on the soil microbiome. These treatments were compared to three controls, the microbial profile of the soil prior to application of copper products, a water application, and spiking the soil with a soilborne phytobacterium, Ralstonia solanacearum (RS). The RS treatment was included to determine if downstream analysis could detect the artificial inoculation. Utilizing multiple ß diversity measurements, each emphasizing various tenets of ecology, provided a greater perspective of the effects the treatments had on the microbiome. Analysis of HTS data revealed that the two treatments containing field applied rates of metallic copper, CS 200 and Cu+Man, had the largest impact on the soil microbiome at seven-days posttreatment compared to water. However, we simulated field applied rates of CS 200 entering the soil by treating soil with CS 2 and determined this concentration had a negligible effect on the soil microbiome.