Abstract
Bacterial spot of tomato, caused by Xanthomonas perforans, X. euvesicatoria, X. vesicatoria and X. gardneri, is a major disease, contributing to significant yield losses worldwide. Over dependence of conventional copper bactericides over the last decades has led to the prevalence of copper-tolerant strains of Xanthomonas spp., making copper bactericides ineffective. Thus, there is a critical need to develop new strategies for better management of copper-tolerant Xanthomonas spp. In this study, we investigated the antimicrobial activity of a hybrid nanoparticle, copper-zinc (Cu/Zn), on copper-tolerant and sensitive strains. The hybrid nanoparticle significantly reduced bacterial growth in vitro compared to the non-treated and micron-size commercial copper controls. Tomato transplants treated with the hybrid nanoparticle had significantly reduced disease severity compared to the controls, and no phytotoxicity was observed on plants. We also studied the hybrid nanoparticle effect on the bacterial pigment xanthomonadin using Near-Infra Red Raman spectroscopy as an indicator of bacterial degradation. The hybrid nanoparticle significantly affected the ability of X. perforans in its production of xanthomonadin when compared with samples treated with micron-size copper or untreated. This study sheds new light on the potential utilization of this novel multi-site Cu/Zn hybrid nanoparticle for bacterial spot management.
Highlights
Tomatoes (Solanum lycopersicum) are one of the most important among vegetable crops worldwide[1]
In this study we demonstrated for the first time the potential of a hybrid nanoparticle (Cu/Zn) in managing bacterial spot of tomato incited by copper-tolerant X. perforans
In greenhouse experiments the Cu/Zn hybrid nanoparticle at concentrations above 50 μg/mL unlike copper-mancozeb or copper alone consistently controlled disease compared to the untreated control
Summary
Tomatoes (Solanum lycopersicum) are one of the most important among vegetable crops worldwide[1]. Ideal conditions for disease occurrence and spread are especially true in tropical and sub-tropical regions of the world including Florida, the leading US state in fresh market tomato production[2,8,9], where climatic conditions of high humidity during the two growing seasons in the year that favor the disease occurrence and spread Prevention strategies, such as clean seed, weed control, sanitation of equipment, and the use of tolerant varieties while important, has only proven to be minimally effective, especially in tropical and subtropical regions[9]. ASM works by activating plant defense systems to increase transcription of pathogenesis-related genes It is reliable under field conditions, disease control with ASM has not been associated with improved yield[19,20,21]. It was shown nano sized particles of Cu2O had bactericidal activity against a copper-tolerant Xanthomonas spp. strain, while micron sized copper hydroxide did not had bactericidal activity at the same concentration of Cu when tested in vitro
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