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 Central Florida; JONES, JEFFREY - University Of Florida; Hong, Jason; PARET, MATHEWS - University Of Florida; GOSS, ERICA - University Of Florida

Submitted to: The ISME Journal: Multidisciplinary Journal of Microbial Ecology
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., Goss, E. 2022. Simulated leaching of foliar applied copper bactericides on the soil microbiome utilizing various beta diversity resemblance measurements.. The ISME Journal: Multidisciplinary Journal of Microbial Ecology. https://doi.org/10.1128/spectrum.01481-21.
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: Nanotechnology-based elemental composites are gaining popularity for their potential applications in agriculture, such as enhancing the antimicrobial activity of bactericides. However, little is known about the potential impact of these composites on soil microbial communities, which could influence soil health and plant productivity. The goal of the reported study was to determine the potential effect of three advanced Cu composites (CS, MV, and FQ) on the soil microbiome dynamics when compared to a conventional copper bactericide (micron-sized copper (Cu)) alone or in combination with the fungicide mancozeb (Cu+Man). Soil samples collected at two different time points from a tomato production field were treated with: copper composites and micron-sized copper suspensions at 2 or 200 µg/ml, Cu+Man at 540 µg/ml, a suspension of Ralstonia solanacearum (RS), or sterile deionized water which served as a water control. Soil samples were collected at 1- and 7-days post treatment (DPT) and were compared to non-treated soil 0 DPT samples. The bacterial populations were compared by extracting DNA and differentiating initially by length heterogeneity polymerase chain reaction(LH-PCR). LH-PCR analysis identified significant shifts in the soil microbiome following treatment with CS (CS 200; 200 µg/ml of metallic Cu), Cu+Man, and RS when compared to the nontreated and water controls, and these samples were then selected for high-throughput sequencing (HTS) analysis of 16s ribosomal deoxyribonucleic acid (rDNA). Using multiple resemblance measures and pairwise comparisons of the HTS data, it was determined that CS 200 and Cu+Man had the largest impact on the soil microbiome at 7 DPT compared to water. Interestingly, resemblance measures that included total abundance or emphasis on rare taxa, Euclidean and Chi squared respectively, revealed that water and RS were significantly different from each other. These novel nanotechnology-based copper composites had very little impact on the soil microbiome when compared to the commercial copper bactericide, but differed significantly from water alone unless diluted.