Photodynamic method of inhibiting growth of a microbial plant pathogen
Inventors
France, Christopher Brian • Bell, William
Assignees
Publication Number
US-12108756-B2
Publication Date
2024-10-08
Expiration Date
2039-09-24
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Abstract
We describe methods and materials for inhibiting the growth of a microbial pathogen of a plant. The method comprises the steps of applying to the plant a combination of a dye-bearing compound which is a reactive oxygen species photosensitizer; and a copper compound, which increases the microbial lethality of the dye-bearing compound towards the microbial pathogen; and exposing the plant to light to activate the combination of the dye-bearing compound and the copper compound and inhibiting growth of a microbial pathogen of a plant. The combination of the dye-bearing compound and the copper compound may result in a synergistic ability to reduce the growth of a plant pathogen.
Core Innovation
The invention provides methods and materials for inhibiting the growth of a microbial pathogen of a plant by applying a combination of a dye-bearing compound, which functions as a reactive oxygen species photosensitizer, and a copper compound to the plant, followed by exposing the plant to light to activate the combination. This combination is disclosed to result in a synergistic ability to reduce plant pathogen growth beyond the effects of either agent alone.
The problem addressed is that existing photodynamic inhibition techniques for plant pathogens often have low effectiveness when used alone or rely on chemicals incompatible with organic agricultural practices, while copper compounds applied as pesticides can cause resistance in pests and present environmental hazards due to the need for high concentrations. The rapid reactivity of oxidizing antimicrobials also limits their sustained effectiveness, requiring frequent re-application, and the use of high-concentration copper solutions can leave undesirable residues on crops and affect their value.
The core innovation is a method that significantly enhances the microbial lethality of photosensitizers through the addition of small, but synergistically effective, amounts of copper compounds, such as copper salts or copper ion-bearing organic complexes, activated by light. The copper and dye-bearing compounds are applied to plants, either simultaneously or sequentially, and in concentrations low enough to be consistent with organic standards and regulatory requirements. Optional additions, such as ascorbate, can further improve effectiveness, and the invention encompasses the use of various adjuvants to enhance delivery or efficacy.
Claims Coverage
The patent contains two main independent inventive features, both centering on the synergistic inhibition of plant microbial pathogens using a photosensitizer dye and a copper compound, and the specific implementation of these methods.
Synergistic inhibition of plant microbial pathogens using a photosensitizer and copper compound activated by light
A method comprising applying to a plant a combination that includes: - A dye-bearing compound which is a reactive oxygen species photosensitizer, provided at a concentration between about 1 and 100 ppm on a mass basis. - A copper compound (e.g., copper salt or copper ion-bearing organic complex) provided at a concentration between about 3.98 and 39.8 ppm of copper on a mass basis. After application, the plant is exposed to light to activate the combination and inhibit microbial pathogen growth. The copper and dye-bearing compound are provided in amounts that are synergistically effective (i.e., the combined effect exceeds the sum of separate effects) to inhibit the pathogen.
Combination of copper salt and photosensitizer dye achieving log kill synergy over additive efficacy models
A method wherein a copper salt and a dye-bearing photosensitizer are used in synergistically effective amounts that increase microbial pathogen log kill by at least 1 order of magnitude over the expected additive efficacy. The additive efficacy model determines expected percent kill as P = X + Y(100−X)/100, where X is the kill percent by the photosensitizer alone and Y is the kill percent by copper salt alone. The actual observed kill exceeds this by at least 1 log, demonstrating synergy.
In summary, the claims cover methods for the synergistic inhibition of microbial pathogens on plants using a combination of a reactive oxygen species photosensitizer and a copper compound, activated by light. The inventive coverage includes critical concentration ranges, forms of copper compounds, and the required synergistic effectiveness as defined by exceeding additive antimicrobial models.
Stated Advantages
The method uses significantly lower concentrations of copper compounds, reducing potential environmental hazards and avoiding unwanted damage to plants or the environment.
By achieving a synergistic antimicrobial effect, the method provides dramatically increased effectiveness in inhibiting plant microbial pathogens, often by several orders of magnitude greater than additive effects.
The approach is compatible with organic agricultural practices and uses compounds that are generally recognized as safe (GRAS), such as riboflavin and certain copper salts.
The photodynamic inhibition method is less likely to result in resistance development in target organisms due to its mode of action involving reactive oxygen species.
Lower concentrations of active ingredients result in fewer, if any, residues left on crops, helping preserve crop value and quality.
Documented Applications
Photodynamic inhibition of bacterial, fungal, algal, cyanobacterial, and viral pathogens on plants.
Treatment and prevention of microbial pathogens in non-woody crop plants, woody plants, turfgrass, fruit-bearing trees, nut-bearing trees, and ornamental plants.
Controlling plant diseases caused by pathogens such as Alternaria solani, Botrytis cinerea, Sclerotinia homoeocarpa, and Xanthomonas hortorum pv. pelargonii.
Application in both indoor (including greenhouses) and outdoor agricultural settings, using natural or artificial light sources.
Use as either a preventative method or as a treatment for plants already infected with microbial pathogens.
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