Myrtle rust is devastating Australian forests: New high-tech spray holds out hope for native trees

Around a decade ago, an invasive fungal disease called myrtle rust reached Australia and began to spread like a plague through certain plants. The disease affects plants of the Myrtaceae family, which includes eucalypts, ...

In only a few years, myrtle rust has changed ecosystems by destroying trees and their canopies, wiped out whole species in certain areas, and taken an economic toll on industries that grow trees such as lemon-scented myrtle and tea tree. The disease is a slow-moving ecological wrecking ball: surveys suggest it may drive at least 16 species of rainforest tree to extinction in the wild within a generation, with another 20 species at risk.

We have used RNA technology similar to that in COVID vaccines to create a highly targeted treatment for myrtle rust: a spray that can restore even severely infected trees to health in around six weeks. Our study was published in Communications Biology . At-risk species in remote places The current approaches to dealing with tree diseases are limited. We can apply fungicides with a scorched-earth policy to kill all fungi , or we can breed plants for resistance to the pathogen.

One-to-two-year-old Syzygium jambos trees (n = 6) grown under glasshouse conditions were treated with nuclease-free H 2 O (negative control), a non-specific dsRNA control (green fluorescent protein (GFP)), or A. psidii-specific dsRNAs beta-tubulin (β-TUB), or transcription elongation factor (EF1-a) at 100 ng/μL and challenged with A. psidii urediniospore inocula 48 h post-dsRNA treatment. Disease was assessed two weeks post-inoculation. a Photo comparison of S. jambos trees, one from each treatment and control group. -dsRNA and GFP control trees showed severe symptoms of myrtle rust, whereas EF1-a and β-TUB-treated plants showed significantly reduced symptoms. Photos were taken two weeks post-inoculation. Credit: Communications Biology (2023). DOI: 10.1038/s42003-023-05618-z Read more

Untreated (left) and treated (right) myrtle rust spores on artificial leaves (upper) and Syzygium jambos(rose apple) leaves (lower), 24 hours after infection. Untreated spores have germinated and produced infection structures that are used to penetrate into the leaf. Treated spores either do not germinate at all, or they are unable to produce the infection structures needed to.penetrate the leaf. Credit: Degnan et al , Communications Biology (2023). DOI: 10.1038/s42003-023-05618-z, CC BY Read more

Untreated (left) and treated (right) Syzygium jambos (rose apple) trees six weeks after infection with myrtle rust. Two weeks after infection, treated plants were sprayed with double-stranded RNA targeting.myrtle rust. Six weeks after infection, the treatment has successfully inhibited myrtle rust and treated plants have re-grown and recovered to a healthy state. Credit: Degnan et al , Communications Biology (2023). DOI: 10.1038/s42003-023-05618-z, CC BY Read more