Date:
May 31, 2017
Source:
Case Western Reserve University
Summary:
Nematodes cause $157 billion in crop damage annually,
largely because traditional pesticides fail to reach plant roots, where the
round worms do their damage. In the lab, tobacco mild green mosaic virus
nanoparticles carrying a nematicide dispersed better when applied to the soil
surface, resulting in more nematicide reaching the root level. The strategy
could decrease the amount of pesticides applied to crops, reducing the risk of
runoff, the amount of chemicals in produce and grains, and the overall cost of
nematode control.
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This image shows roots of a corn
plant infected by endoparasitic nematodes (in red). The plant is being treated
with a pesticide (purple sphere) encapsulated into Tobacco mild green mosaic
virus (grey rods). The virus enhances the diffusion of the pesticide to the
root level of the plant, where the nematode resides, thus increasing treatment
efficacy.
Credit: Paul Chariou
Researchers at Case Western Reserve
University are applying drug-delivery technology to agriculture to control
parasitic roundworms more effectively and safely.
The tiny roundworms, or nematodes,
cause $157 billion in crop failures worldwide each year, other researchers
estimate, largely because they're beyond the reach of pesticides. The chemicals
disperse poorly into soil, while the parasites feed at plant roots well below
the surface.
As a result, farmers apply large
amounts of pesticides, which can increase the chemical concentrations in food
or run off and damage other parts of the environment, all of which have costs.
But biomedical engineering
researchers at Case Western Reserve may have found an effective solution.
"We use biological
nanoparticles -- a plant virus -- to deliver a pesticide," said Paul
Chariou, a PhD student in biomedical engineering at Case Western Reserve and
author of a study on the process published in the journal ACS Nano.
"Use of the nanoparticle increases soil diffusion while decreasing the
risk of leaching and runoff, reducing the amount of chemical in food crops and reducing
the cost to treat crops."
Chariou worked with Nicole
Steinmetz, the George J. Picha Professor in Biomaterials appointed by the Case
Western Reserve School of Medicine.
Parasitic nematodes feed on a wide
range of crops, including corn, wheat, coffee, soybeans, potatoes and a host of
fruit trees. Damage they cause at the roots impairs the plants' ability to
absorb water and nutrients, which can kill young plants and reduce yields in
mature plants.
To try to deliver more pesticide to
the roots, the researchers used tobacco mild green mosaic virus (TMGMV). The
virus is used in Florida as a pesticide to control an invasive weed, but is
benign to nematodes.
TMGMV can infect tomatoes, eggplant
and other solenaceous plants, but is not a threat to nearly 3,000 other plant
species that suffer nematode infections.
The virus self-assembles into a
tube-like structure, 300 nanometers long by 18 nanometers wide, with a hollow
channel 4 nanometers wide.
As a proof of concept for this
study, the researchers tested the plant virus-derived nanoparticles with a
nematicide called crystal violet, which has been used to kill nematodes on skin
but not in agriculture.
The researchers capitalized on
surface chemistry to load the positively charged crystal violet molecules into
the negatively charged channel of the virus-nanoparticle. Each virus particle
carried about 1,500 crystal violet molecules.
In lab experiments with conditions
mimicking crop soils with a pH of 5, the nematicide remained attached as the
virus particles were applied to and diffused through the soil. "At the
root level, the nematicide diffuses out of the virus over time," Chariou
said. Warmer and more acidic soils caused the chemical to be released faster.
In testing with the nematode Caenorhabdiis
elegans, in a liquid culture, the scientists confirmed that nematodes were
paralyzed and killed by treatment with the drug-infused virus-nanoparticle --
this is because the drug diffuses out of its carrier over time allowing it to
interact with the nematodes. As a secondary killing mechanism, the researcher
also noted that the roundworms were eating the nanoparticles. The crystal
violet was released in the animals' stomachs, paralyzing and killing them.
Most importantly,
nematicide-carrying virus particles dispersed better when applied to the soil
surface and made more molecules available to kill nematodes at the root level.
Chariou and Steinmetz are now
testing the delivery system using chemical pesticides approved for crops and
developing a computer model to better understand and, ultimately, optimize the
nanoparticle's ability to diffuse through soil.
Story Source:
Materials provided by Case Western Reserve
University. Note: Content may be edited for
style and length.
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