RNA-based spray combats myrtle rust in plants

Researchers at The University of Queensland (UQ) have developed a treatment that can both prevent and cure infection caused by an invasive fungal disease devastating native Australian plants.

As explained by UQ’s Dr Anne Sawyer, myrtle rust has become a problem for popular native Myrtaceae species like eucalypts, lilly pilly and paperbark since it was detected in NSW in 2010. “It has since spread all the way up the east coast and into the Northern Territory, as well as Western Australia and even New Zealand,” she said.

“The symptoms of infection range from leaf spots of yellow fungal spores through to death of the tree, even large old trees.

“There are more than 2000 species of Myrtaceae native to Australia, with 16 species of rainforest trees on the east coast facing extinction due to this disease.”

Together with PhD candidate Rebecca Degnan and Professor Neena Mitter, Sawyer worked with the Queensland Government Department of Agriculture and Fisheries to develop an environmentally friendly spray that uses RNA technology to treat plants infected by myrtle rust. Their results, published in the journal Communications Biology, found that the spray acts both preventively and curatively against myrtle rust disease.

“We found that when the double-stranded RNA was applied to a healthy tree, it prevented the plant from being infected,” Degnan said.

“What’s even more exciting [is], when we infected the plants and applied the double-stranded RNA as late as two weeks post infection, the plants recovered.

“It’s significant because our previous studies didn’t have that curative aspect, so being able to apply a treatment after infection gives it more potential.”

Having so far only conducted short-term experiments up to six weeks after infection, Sawyer said the team will now test the RNA treatment in field trials in order to better assess the spray’s longevity. “We also want to see whether the plants are protected from a second infection and if the RNA can protect new growth after the leaves are sprayed,” she said.

While Degnan acknowledged that the treatment is not necessarily a silver bullet, the researchers believe their findings have immediate potential in the management of the epidemic of myrtle rust in Australia.

Image shows leaves infected with myrtle rust. Image ©Megan Pope, UQ.