A project undertaken at The University of Queensland, and supervised by Anne Sawyer
Myrtle rust is an invasive plant disease threatening native Australian plants in the Myrtaceae family including lemon myrtle, tea-tree, eucalypts and lilly-pillys. These iconic trees make up 10% of Australia’s native flora and are of considerable significance to indigenous culture and industry (native forestry, cut flower, essential oils, honey, native foods).
Myrtle rust, caused by the fungal pathogen Austropuccinia psidii, arrived in Australia in 2010 and has pushed many native species to the brink of extinction putting whole ecosystems at risk including world heritage listed Lord Howe Island, Gondwana Rainforests, K’gari (Fraser Island) and the Wet Tropics.
Figure 1.
Myrtle rust is controlled in nurseries and plantations with fungicides, however, these are harmful to humans and the environment, making them unsuitable for large-scale use in natural systems. A new solution which is effective, but environmentally, culturally, and economically responsible, is urgently needed.
RNA-based biopesticides are an environmentally friendly, cutting-edge alternative to chemical pesticides. The active ingredient is pathogen-specific double-stranded RNA (dsRNA), which can be sprayed onto plants to trigger a natural defence mechanism known as RNA interference (RNAi) in the pathogen, silencing essential pathogen genes and inactivating the pathogen preventing infection.
Figure 2.
We have developed RNA biopesticides against myrtle rust, however, for product development a significant increase in efficacy is needed. This requires a better understanding of the RNAi mechanism in A. psidii. In this project, we will characterise RNAi in A. psidii by conducting small RNA sequencing to identify the small RNAs produced from A. psidii-specific dsRNA. We will then train AI models to design improved RNAi constructs.
The anticipated outcome is the development of an RNA biopesticide against myrtle rust, which will provide a new solution to the more than 10-year epidemic of myrtle rust in Australia. This will benefit Australia’s native plant industries and offers a lifeline to Australia’s 400 iconic Myrtaceae species currently at risk.