Mangos are an important industry in northern Australia and affected by mango dieback associated with various members of the Botryosphaeriaceae. The Botryosphaeriaceae family contains about 24 genera and 222 species worldwide, on a diverse range of host plants. These fungi are primary and latent pathogens.  

The fungal family: The Botryosphaeriaceae commonly colonise woody host plants as endophytes and express pathogenicity following host stress leading to disease symptoms such as twig, branch and stem cankers, dieback, and fruit rot. Tree symptoms can lead to a loss of productivity and tree death. Changing climatic conditions and horticultural practices such as deficit-irrigation contribute to elevated tree stress leading to increased disease expression from latent infecting pathogens. Understanding the emerging biosecurity risks of latent pathogens threatening tree crop productivity due to changing climate is of vital importance.  

Effect on mango: Within this fungal family, the Lasiodiplodia species are of interest because they are commonly associated with mango dieback worldwide. Using a Lasiodiplodia species as a model, this project will explore infection biology and disease expression in mango.  

Host-fungus interactions: The host-fungus interactions will be investigated using in-planta experiments and transcriptomics. Gaining an understanding of the infection biology, and how and why Lasiodiplodia switches from an endophytic to pathogenic lifestyle and the factors that contribute to disease expression in mango trees will inform the development of improved disease management strategies. 

Aim: The aim of this project is to explore infection biology of Lasiodiplodia species and resulting disease expression in mango. 

Approach: The project will investigate the following, with the option for the student to introduce their own spin and ideas into the project: 

• Infection and colonisation: Glasshouse experiments using mango plants in pots to explore the biology and pathogenicity of Lasiodiplodia species.  
  Where and how does infection occur, and how extensive is colonisation?   
  What is required for the endophyte to become pathogenic? What combination of potential plant stressors (eg. wound, water-deficit, plant growth retardant, heat) are required for the endophyte to become pathogenic?    
• Host – fungus – environment interaction: Using a transcriptomic approach various questions can be asked eg: 
  a. How does host recognition function for an endophyte?
  b. Does plant stress affect host receptor expression, or fungal effector expression, or both? Ie Identify mechanism switch from endophyte to pathogen. 
• Disease management: Utilising the increased understanding of the mechanics of pathogenicity gained through the previous chapters, explore, design, and field test mango dieback disease management strategies. Are there ways to reduce infection, colonisation, or disease expression?

People: The PhD student for this project will be starting in coming months. Also on this project are:

Professor Benjamin Schwessinger, The Australian National University.
Professor Celeste Linde, The Australian National University.
Stanley Belgrade, Sonu Yadav, and Sharl Mintoff, Northern Territory Department of Agriculture and Fisheries (NT DAF).

Questions? Questions about this project can be directed to Sarah Adams, Chief Operating Officer, at plantbiosecurity@anu.edu.au or +61 459 341 281.