@article{liao_huang_carvalho_choudhary_da silva_colee_huerta_vallad_freeman_jones_et al._2021, title={Magnesium Oxide Nanomaterial, an Alternative for Commercial Copper Bactericides: Field-Scale Tomato Bacterial Spot Disease Management and Total and Bioavailable Metal Accumulation in Soil}, volume={55}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.1c00804}, abstractNote={Copper (Cu) is the most extensively used bactericide worldwide in many agricultural production systems. However, intensive application of Cu bactericide have increased the selection pressure toward Cu-tolerant pathogens, including Xanthomonas perforans, the causal agent of tomato bacterial spot. However, alternatives for Cu bactericides are limited and have many drawbacks including plant damage and inconsistent effectiveness under field conditions. Also, potential ecological risk on nontarget organisms exposed to field runoff containing Cu is high. However, due to lack of alternatives for Cu, it is still widely used in tomato and other crops around the world in both conventional and organic production systems. In this study, a Cu-tolerant X. perforans strain GEV485, which can tolerate eight tested commercial Cu bactericides, was used in all the field trials to evaluate the efficacy of MgO nanomaterial. Four field experiments were conducted to evaluate the impact of intensive application of MgO nanomaterial on tomato bacterial spot disease severity, and one field experiment was conducted to study the impact of soil accumulation of total and bioavailable Cu, Mg, Mn, and Zn. In the first two field experiments, twice-weekly applications of 200 μg/mL MgO significantly reduced disease severity by 29-38% less in comparison to a conventional Cu bactericide Kocide 3000 and 19-30% less in comparison to the water control applied at the same frequency (p = 0.05). The disease severity on MgO twice-weekly was 12-32% less than Kocide 3000 + Mancozeb treatment. Single weekly applications of MgO had 13-19% higher disease severity than twice weekly application of MgO. In the second set of two field trials, twice-weekly applications of MgO at 1000 μg/mL significantly reduced disease severity by 32-40% in comparison to water control applied at the same frequency (p = 0.05). There was no negative yield impact in any of the trials. The third field experiment demonstrated that application of MgO did not result in significant accumulation of total and bioavailable Mg, Mn, Cu, or Zn in the root-associated soil and in soil farther away from the production bed compared to the water control. However, Cu bactericide contributed to significantly higher Mn, Cu, and Zn accumulation in the soil compared to water control (p = 0.05). This study demonstrates that MgO nanomaterial could be an alternative for Cu bactericide and have potential in reducing risks associated with development of tolerant strains and for reducing Cu load in the environment.}, number={20}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Liao, Ying-Yu and Huang, Yuxiong and Carvalho, Renato and Choudhary, Manoj and Da Silva, Susannah and Colee, James and Huerta, Alejandra and Vallad, Gary E. and Freeman, Joshua H. and Jones, Jeffrey B. and et al.}, year={2021}, month={Oct}, pages={13561–13570} }
 @article{adhikari_adhikari_timilsina_meadows_jones_panthee_louws_2019, title={Phenotypic and Genetic Diversity of Xanthomonas perforans Populations from Tomato in North Carolina}, volume={109}, ISSN={["1943-7684"]}, url={http://dx.doi.org/10.1094/phyto-01-19-0019-r}, DOI={10.1094/PHYTO-01-19-0019-R}, abstractNote={Bacterial spot caused by Xanthomonas spp. is one of the most devastating diseases of tomato-producing regions in North Carolina (NC). Among 293 strains collected from tomato in NC in 2015 and 2016, 290 strains were analyzed in vitro copper and streptomycin sensitivity assays and data revealed that over 95% of the strains were copper tolerant in both years while 46% and 25% were streptomycin tolerant in 2015 and 2016, respectively. Using BOX repetitive element polymerase chain reaction (BOX-PCR) assay, fingerprint patterns showed four haplotypes: H1, H2, H3, and H4 among the strains analyzed. The multiplex quantitative real-time polymerase chain reaction (qPCR) on a subset of representative strains (n = 45) targeting the highly conserved hrcN gene identified Xanthomonas strains from tomato in NC belonged to X. perforans. Race profiling of the representative strains (n = 45) on tomato and pepper differentials confirmed that approximately 9% and 91% of strains are tomato races T3 and T4, respectively. Additionally, PCR assays and sequence alignments confirmed that the copL, copA, and copB (copLAB copper tolerance gene cluster) and the avrXv4 genes are present in the strains analyzed. Phylogenetic and comparative sequence analysis of six genomic regions: elongation factor G (fusA), glyceraldehyde-3-phosphate dehydrogenase A (gapA), citrate synthase (gltA), gyrase subunit B (gyrB), ABC transporter sugar permease (lacF), and GTP binding protein (lepA) suggested that 13% and 74% of X. perforans strains from NC were genetically similar to races T3 and T4 from Florida, respectively. Our results provide insights into bacterial spot management strategies in tomato should focus on deploying resistance genes to combat emerging pathogenic races of X. perforans and overcome the challenges currently posed by intense use of copper-based bactericides.}, number={9}, journal={PHYTOPATHOLOGY}, author={Adhikari, Pragya and Adhikari, Tika B. and Timilsina, Sujan and Meadows, Inga and Jones, Jeffrey B. and Panthee, Dilip R. and Louws, Frank J.}, year={2019}, month={Sep}, pages={1533–1543} }