Soybean leaf infected with leaf disease

[Image above] Soybean leaf infected with leaf disease. Silver-based nanoparticles could serve as an alternative method to protect plants from pathogens in the future. Credit: International Institute of Tropical Agriculture, Flickr (CC BY-NC 2.0)

Sticker shock is to be expected when walking into an upscale clothing or jewelry store. Yet more and more, food staples are feeling like the new luxury items.

Since 2021, food prices have outpaced general inflation, increasing a jaw-dropping 11% from 2021 to 2022 in the United States—the largest annual increase in more than 40 years. The reasons for these sky-high prices are complex, but it largely boils down to the fact that food is a global, not local, supply chain.

Almost every large supermarket or grocery store chain relies on food items sourced from hundreds or thousands of miles away. When global events occur, such as the COVID-19 pandemic or the ongoing war in Ukraine, it is no longer simple or even possible sometimes to import these items, leading to a shortage and increased prices.

While federal agencies anticipate that the rate of grocery inflation will decelerate in 2024, there are other events looming on the horizon that are expected to significantly impact the global food supply chain. For example, the increasing risk of plant diseases.

Plant diseases, which prevent plants from performing to their maximum potential, are strongly influenced by host biodiversity, spatial structure, and abiotic conditions. All these factors are undergoing rapid changes as “the climate is warming, habitats are being lost, and nitrogen deposition is changing nutrient dynamics of ecosystems with ensuing consequences for biodiversity,” an open-access paper explains.

To date, agriculture and livestock management has relied largely on antimicrobial drugs to prevent plant pathogens, such as bacteria, fungi, and viruses, from causing diseases. But this overreliance on drugs in farming is driving antimicrobial resistance, just as it is in healthcare settings.

For this reason, alternative methods are needed to protect plants from pathogens. A recent review article explores the potential of silver-based nanoparticles to serve this purpose.

The authors come from several institutions in the Republic of Korea, Qatar, and India. In the review, they consider recent advancements, current limitations, and future perspectives on using silver-based nanoparticles to combat plant diseases. Some highlights from the 27-page paper are given below.

Silver: An established antimicrobial agent

It is well established in the literature that silver nanoparticles display exceptional broad-spectrum antimicrobial mechanisms. But even before people fully understood how silver worked as an antimicrobial, the metal was used to prevent the growth of dangerous germs, such as by dropping silver coins into water and wine casks during long ocean voyages.

With advances in nanoengineering, researchers have improved the stability, controlled release, and targeted delivery mechanisms of silver-based nanoparticles. Additionally, the versatility of the nanoparticles’ antimicrobial mechanisms “further minimizes the likelihood for bacterial pathogens to develop resistance, thus positioning them as an attractive alternative to conventional antibiotics and pesticides,” the authors write.

Bioresources for green synthesis of silver-based nanoparticles

Researchers have explored a wide array of bioresources for the green synthesis of silver-based nanoparticles, including bacteria, fungi, algae, plant extracts, and several biopolymers. Table 1 in the paper provides an extensive list of these various organisms, but some examples from this list are

Silver-based nanoparticles combat bacterial, fungal, and viral phytopathogens

Sections 6, 7, and 8 of the paper summarize studies that investigated the use of silver-based nanoparticles to combat bacterial, fungal, and viral phytopathogens, respectively. The authors recommend that future research should focus on detailing the specific molecular events underlying the nanoparticles’ antimicrobial mechanisms to further maximize their potential.

Potential negative impacts of silver-based nanoparticles on plant health

As nanomaterial engineering and technology have advanced, concerns about the potential negative impacts of nanoparticles on human health have grown as well. For example, consider the recent ban on titanium dioxide as a food additive in the European Union.

Studies show that silver-based nanoparticles can have both positive and negative effects on plants, too, depending on numerous biotic and abiotic factors (see here and here). In addition, excessive use of these nanoparticles may have cytotoxic effects on beneficial soil microorganisms, as well as interfere with essential soil functions, such as nutrient cycling and organic matter decomposition.

For these reasons, the authors stress that silver-based nanoparticles should be used in a controlled manner “to balance their promising capabilities with environmental concerns.”

The paper, published in Science of The Total Environment, is “Bioinspired silver nanoparticle-based nanocomposites for effective control of plant pathogens: A review” (DOI: 10.1016/j.scitotenv.2023.168318).