Project Leader

Michelle Moffitt, Western Sydney University




Many species of Myrtaceae exhibit varying sensitivity to infection by Austropuccinia psidii, placing many vulnerable Australian ecosystems at risk of decline. More research is needed to identify the defenses that enable some plants to resist A. psidii infection so that we can survey priority species in the field for resistant populations and prioritise germplasm collection. Small molecules called ‘metabolites’ which elicit these defenses in resistant plants can be detected by metabolomics methods. Our preliminary work has established that prior to infection resistant germplasm from the species Melaleuca quinquinervia contain metabolic signatures that differentiate them from hypersensitive and susceptible phenotypes.

Objectives and Impact

Objectives: Employ metabolomics across a diverse selection of Myrtle Rust Action Plan priority species to establish a set of biomarkers that rapidly identify resistant plants without infection trials or previous genomic knowledge.

Methods: We will harvest pre-infected leaf tissue from plants obtained from the Royal Botanical Gardens, Mount Annan, spanning 12 genera of Myrtaceae and employ our established metabolomics pipeline.  Concurrently, we will infect these plants with A. psidii and determine the plant response to infection.  We will combine these data, to refine and ratify a list of key metabolites identified in project PBSF023 as biomarkers that putatively predict resistance to A. psidii infection. We will then optimise our protocols to capture these biomarkers from wild-collected samples.

  • Outputs:
  • Improved understanding of the biochemistry responsible for resistance to A. psidii
  • Curated set of biomarkers to assess individual plants within selected Myrtaceae species for levels of resistance/tolerance
  • Optimised protocols for field collections to enable rapid metabolomic-based field surveys of A. psidii resistance

Outcomes/Impact: Significant contribution toward assessment of resistance in a diverse set of genera for rapid field surveys (Action 3.2.3), to inform breeding strategies (Action 4.3.1),  screening for germplasm capture (Action 4.1.1), and contribute to understanding of resistance  (Action 4.3.3).


In the progress report, the authors present the achievement of the three milestones:

1. Harvesting and infection of plant material

We have collected species belonging to eight tribes of the Myrtoideae subfamily of Myrtaceae, including species listed as priority species in the Myrtle Rust Action Plan (2020). Twenty replicates of each species were inoculated with A. psidii and their susceptibility to the infection was recorded. In some instances, additional field collections were obtained from the Royal Botanical Gardens Mount Annan living collection. We have confirmed our metabolomics methods from PBSF027 are suitable for differentiating resistant and susceptible phenotypes in Eucalytpus grandis.  We have also trialled protocols to optimise the collection of leaf material from field sites without the loss of critical metabolomics biomarkers.

2. Use of social media

Our project has been successful in the use of communication techniques on social media, including Twitter and Facebook to raise concern about the myrtle rust pandemic in Australia.

3. Involvement of early career researchers

This project has employed the use of three early career researchers and has highlighted the issues of biosecurity and myrtle rust to undergraduate students at Western Sydney University.

A copy of the progress report can be viewed here.