Could drought stress impact disease resistance?

The team at APPN’s Australian National University (ANU) Node in Canberra have been contributing to a fascinating project led by the Research Centre for Ecosystem Resilience (Botanic Gardens of Sydney). The project is studying how drought stress affects resistance to the disease Myrtle rust (Austropuccinia psidii) in broad-leaved paperbark trees (Melaleuca quinquenervia).

Myrtle rust is a fungal disease from South America that was first detected in New South Wales in 2010. It has since spread across eastern Australia and over 380 native hosts have been identified. The disease affects plants in the Myrtaceae family, which is the largest plant family in Australia and provides vital food, shelter and habitat for countless animal species. 

Paperbark trees appear to have varying degrees of natural resistance to Myrtle rust disease and the Sydney Botanic Gardens project includes the development of a high-throughput genotyping method to identify resistant individuals.

For now, however, APPN’s contribution has focused on increasing understanding of how drought stress might interact with this natural Myrtle rust disease resistance. 

Botanic Gardens researcher Karina Guo has used an APPN LI-COR LI-600 porometer to measure osmotic conductance in individual paperbark seedlings that were grown under different drought treatments. This phenotyping technology allowed Karina to accurately map subtle variations in the drought conditions experienced by each plant.  

The handheld LI-600 measures stomatal conductance and chlorophyll fluorescence simultaneously with location and leaf angle data for individual leaves. The measurements are also quick, making it possible to screen large populations within a short time frame. 

While habitat restoration is helping to mitigate threats like Myrtle rust, it is critically important that these restoration efforts will be resilient to known future threats such as drought. Urban development, climate change and shifts in water use can all impact on areas of paperbark habitat and are thought to induce responses similar to drought stress.

It is hoped the drought experiment will improve understanding of the interplay between disease resistance and drought stress, so that restoration practitioners such as Landcare can incorporate the knowledge into their plans.

The project is being supported by the Research Centre for Ecosystem Resilience at the Botanic Gardens of Sydney. Karina is additionally supported by a Research Training Program scholarship from The University of Sydney.

8 April 2025