Austraalia: RNA shows biopesticide potential in canola, cotton trials

Susan Webster, September 4, 2023

Grain Central

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Verticillium is a fungus which affects plants including cotton, and has potential to be controlled by dsRNA. Photo: Chris Brosnan, QAAFI

MEDICAL technology that developed a speedy vaccine for COVID is now offering promise as a potential biopesticide for crops.

Queensland-based molecular biologists are looking at harnessing movement by a form of ribonucleic
acid (RNA) which delivers the DNA’s genetic instructions to a cell.

Plant geneticists at the University of Queensland are focussing on how forms of RNA can enhance plant protection and fight pests, viruses and fungal infections.

Recent research was detailed in a talk on Tuesday by Chris Brosnan, a research fellow and senior  research officer at the Queensland Alliance for Agriculture and Food Innovation’s Centre for Horticultural Science.

His work on canola, cotton and tomatoes is revealing how the RNA travels to various parts of the plant.

QAAFI researcher Dr Chris Brosnan.

“Foliar application of double-stranded RNA (dsRNA)-based biopesticides represents a sustainable alternative to traditional crop protection such as chemical pesticides, fungicides and insecticides,” Dr Brosnan said.

“Sprayed on leaves, the dsRNA enters the leaf vascular system and rapidly moves to the plant’s leaves, stem, flowers and seedhead.

“It also invades the roots.

“From there it appears to be functional against both fungi and viral pathogens. It has also been effective against whitefly.

“The bulk of the applied dsRNA doesn’t enter the plant cells, it goes into the fungus more efficiently.”

Earlier research has shown that topical application of dsRNA proved a very effective in controlling myrtle rust.

The researchers are aiming for an 80 percent benchmark control level against any pathogen.

Research with tomatoes and canola saw good movement throughout the whole plant and some activity in the roots, while cotton plants sprayed overhead also recorded movement down to older leaves.

“After two weeks, we saw intact dsRNA – in other words, it wasn’t a once-off effect.”

However, he said weather conditions could affect take-up.

“We had to add a penetrant to get past the cuticle of a leaf.

“It might change with drought and water stress, it depends on a plant’s water flow.”

The researchers are trying to use AI to train predictive models and hope to amplify its effectiveness.

“That means we could have a single spray which would be far more effective than having to dose it all the time.

“We are also looking at delivery of other RNA structures by using nanoparticles.

“For the first time we have defined the uptake and maintained movement of dsRNA and our research stands to add significant benefit to the emerging field of plant protection.”