Aussie Scientists Protect Crops With Groundbreaking Virus Spray

The environmentally friendly spray is a novel way to protect plants against viruses.

It’s like an invisible shield for your plants. You can’t see it or feel it, but a new spray developed by Australian scientists promises to protect crops against viruses.

Biotechnology researchers at the University of Queensland claim their new invention is an environmentally sustainable alternative to toxic pesticides. A single application of the spray protected tobacco plants from a virus for 20 days, according to their study published this week in Nature Plants.

“It's like a vaccine for viruses on the plant,” says lead author Associate Professor Neena Mitter.

While we have plenty of substances that can protect crops from various pests and fungi, viral diseases are harder to control, says Mitter. There are no treatments to kill viruses directly, and enabling plants to become virus-resistant normally requires genetically modifying the crops.

Plants that are modified to fight off viruses contain bits of the virus’ genetic material, called double-stranded ribonucleic acid (RNA). The pieces are small so they don’t actually cause disease (you would need the complete genome of the virus for that), but they do activate the plant’s natural defence mechanism against the specific virus.

Instead of having to modify the plants, researchers around the world have been looking for ways to simply put the RNA strands directly onto plants where they can do the protective work. But RNA is expensive to produce and degrades really quickly, so you need some way to make it stick.

Now Mitter’s team has achieved exactly that by combining the RNA with nanoparticles of biodegradable clay, a substance developed by her colleague Professor Gordon Xu.

The clay sheets at nanoscale are like minuscule layers of puff pastry, explains Mitter. The clay is positively charged, whereas the RNA fragments are negatively charged, which helps them stick together, creating a protective substance the scientists have dubbed BioClay.

The resulting BioClay powder is then suspended in water and simply sprayed on the plants, providing weeks of protection which degrades very slowly over time and leaves no visible trace.

Artist's impression of the BioClay spray containing nanoparticles with
RNA strands (not to scale).
IMAGE COURTESY NEENA MITTER.

“The layers of puff pastry slowly peel off over time, releasing a little bit of RNA every day, which provides protection for the plant, and after 6-8 weeks there is nothing left,” explains Mitter. The clay can even withstand heavy rains.

"I see this technology as a potential game-changer,” she says. “While we have concentrated only on viral pathogens, this technology should be applicable to all classes of pathogens."

According to Mitter, the invention could even be used in nurseries to spray plants, thus providing farmers with seedlings that are already protected. Next up, the virus spray needs to pass large-scale field tests on various crops, but she believes the commercial potential is there.

The researchers believe the spray will be commercially viable since there’s no need to implement expensive new technology to apply the treatment—existing spraying technology works just fine.

“BioClay has the capacity to change the way we protect plants with the potential of reducing pesticide usage and overcoming the obstacles faced by genetically modified crops,” they write in the paper.

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