Silver Bullet for PTA and Kauri Dieback?

Silver Bullet for PTA and Kauri Dieback?










It could be great news for those fighting PTA, the pathogen killing kauri in unprecedented number in Northern bush. Researchers from the University of Florida Institute of Food and Agricultural Sciences and the New Jersey Institute of technology may have discovered a “silver bullet” that will protect the giant trees from this deadly fungus.

PTA (Phytophthera toxa Agathis) is a fungus that attacks the roots of kauri, often leading to the death of the tree, and so far it has proven resistant to all treatments that could sustain kauri for their often 2000 year lifespans. However, the US based team has found a blend of silver nano-particles and wormwood extract can kill several strains of Phytophthera.

“The silver nanoparticles are extremely effective in eliminating the fungus in all stages of its life cycle,” says research team leader, G. Shad Ali. “In addition, it had no adverse effects on plant growth.”

The silver nanoparticles measure 5 to 100 nanometers in diameter (20 nanometers is about the thickness of a cell wall) and are sprayed onto a plant. They then shield the plant from the fungus. Silver nanoparticles are currently being investigated for applications in various industries, including medicine, diagnostics, cosmetics and food processing. They are already used in wound dressings, food packaging and in consumer products like textiles and footwear for fighting odor-causing microorganisms. Since the silver nanoparticles display multiple ways of inhibiting fungus growth, the chances of pathogens developing resistance to them are minimized, Ali said. Because of that, they may be used for controlling fungicide- resistant plant pathogens more effectively.

The team’s work was published this month in the journal Phytopathology. The abstract of their paper is published below

Ali, M., Kim, B., Belfield, K., Norman, David J., Brennan, M., Shad Ali, G., Inhibition of Phytophthora parasitica and P. capsici by silver nanoparticles synthesized using aqueous extract of Artemisia absinthium, in Phytopathology,

Application of nanoparticles for controlling plant pathogens is a rapidly emerging area in plant disease management, and nanoparticles synthesis methods that are economical and eco-friendly are extensively investigated. In this project, we investigated the potential of silver nanoparticles (AgNPs) synthesized with aqueous extract of Artemisia absinthium L. against several Phytophthora spp., which cause many economically important crop diseases. In in vitro dose-response tests conducted in microtiter plates, 10 µg mL-1 AgNPs inhibited mycelial growth of P. parasitica, P. infestans, P. palmivora, P. cinnamomi, P. tropicalis, P. capsici, and P. katsurae. Detailed in vitro dose-response analyses conducted with P. parasitica and P. capsici revealed that AgNPs synthesized with A. absinthium extract were highly potent (IC50
: 2.1 to 8.3 µg mL-1) and efficacious (100%) in inhibiting mycelial growth, zoospore germination, germ tube elongation, and zoospore production. Interestingly, AgNP treatment accelerated encystment of zoospores. Consistent with in vitro results, in planta experiments conducted in a greenhouse revealed that AgNP treatments prevented Phytophthora infection and improved plant survival. Moreover, AgNP in in planta experiments did not produce any adverse effects on plant growth. These investigations provide a simple and economical method for controlling Phytophthora with AgNP without affecting normal plant physiology.