Fungal diseases of wheat threaten global food security

Fungal diseases are the cause of millions of tonnes in yield losses each on farms around the world. This is serious issue not only in terms of financial losses, but also when considering food security and stability. As an example, the table below outlines losses on Australian wheat farms to disease. The top four diseases in terms of losses are caused by fungal pathogens (based on 2008 prices). Using today's wheat prices, the losses from fungi in Australia exceed $1 billion dollars, and that is using effective control measures; without these losses would exceed $5 billion dollars. Thus there are many good reasons to better understand how these pathogens cause disease!

How do these pathogens cause disease?

Our laboratory focuses on two significant pathogens of wheat.Stagonospora nodorum is a fungus that causes leaf and glume blotch disease on wheat (Septoria nodorum blotch). This disease causes greater than $100 million dollars in yield losses per annum in Australia alone and has been recently ranked as the third most important disease of wheat in this country. Traditional breeding methods for disease controls have only been partially successful at best and new and innovative anti-fungal strategies are required to prevent disease and secure Australian and global wheat supplies in the future.

Not only is S. nodorum a threat to global food security, its also extremely interesting and versatile to work with! S. nodorum can be cultured in the lab and is amenable to many common genetic techniques such as targeted gene disruption and gene overexpression. The genome sequence has been completed and extensive proteomics and metabolomics resources have been developed making S. nodorum a perfect model pathogen to better understand plant-pathogen interactions.

Electron microscope images of Septoria nodorum blotch fungus invading a wheat leaf. Photo: Kasia Clarke, ACNFP

The second wheat pathogen we study in the lab is Zymoseptoria tritici. Z. tritici is the most important pathogen of wheat in Europe, the region that produces one-fifth of the world's wheat supply.Zymospetoria tritici is a fungal pathogen of wheat related to Stagonospora nodorum, and is the causal agent of the most important wheat disease in Europe (Septoria tritici blotch). This single disease alone is responsible for greater than $1 billion dollars in losses each year. The disease is particularly problematic in that natural sources of resistance are difficult to source and the pathogen is very adept at rapidly evolving fungicide resistance.

Interestingly, the disease isn't currently a major problem in Australia. There are many postulated reasons for this including the possibility that European isolates of the pathogen have evolved to be more aggressive. Fortunately, Australian quarantine has prevented these isolates from entering Australia however the pathogen remains a serious biosecurity risk. Our lab is studying all aspects of the above diseases with a focus implementing this improved understanding to facilitate new and novel disease management strategies.

Fungi synthesize an amazing range of novel and active compounds!

Another research area in the lab is focused on understanding fungal secondary metabolism and identifying novel metabolites. Fungal secondary metabolites are among the biologically active compounds on the earth and are part of our daily lives, for good or bad ... . For example, its almost impossible to count how many lives penicillin has saved. More recently, statin-based drugs have an enormous impact of many peoples lives in terms of cholesterol control. However, not all these compounds are beneficial. Many fungi produce compounds that are lethal. Aflatoxin is the worst carcinogenic toxin produced in nature whilst a variety of plant pathogenic fungi produce mycotoxins that render the plant useless to eat (for humans or animals). And who can forget death cap mushrooms!

Recent grants

• Solomon, P.S. (2012) Understanding the production risks from necrotrophic fungi. Grains Research and Development Corporation. $180,000
• Solomon, P.S. (2012) Functional characterisation of the necrotrophic effector proteins Tox1 and Tox3 from the wheat pathogen Stagonospora nodorum. ARC Discovery $350,000.
• Solomon, P.S. (2011) The identification of Mycosphaerella graminicola effectors that promote pathogenicity on wheat. ARC Future Fellowship $803,186.
• Solomon, P.S. (2011) Australian Necrotrophic Fungal Programme. Grains Research and Development Corporation. $500,000 AUD.
• Solomon, P.S., Bringans, S. & Lipscombe, R.J. (2011) The development of mass spectrometry techniques for mapping post-translational modification in the wheat pathogen Stagonospora nodorum. ARC Linkage $90,666.
• Solomon, P.S, Rathjen, J.P., Hardham, A., Jones, D. & Mathesius, U. (2010) An AKTA Avant protein purification system to unravel plant disease. ANU Major Equipment Committee Grant $80,000 AUD.
• AR Hardham, A.R., Kirk, K., Broer, S., Von Caemmerer, S., Mathesius, U., Solomon, P.S., Masle, J., Saliba, K.J., Pogson, B.J., Parish, C.R., Atkin, O.K., Mahalingam, S., Ball, M.C., Tremethick, D.J., Rolph, M., Djordjevic, M.A., Hill, C.E. (2010) Multiphoton confocal microscope. ARC LIEF $600,000 AUD.
• Oliver, R.P. & Solomon, P.S. (2009) Australian Centre for Necrotrophic Fungal Pathogens: Fungal Pathogenicity; Continuation. Grains Research and Development Corporation $473,754 AUD.
• Solomon, P.S., Oliver, R.P. and Lipscombe, R.J. (2008) Investigating a new paradigm for plant-pathogen interactions; Identification of host-selective toxin proteins in the wheat pathogen Stagonospora nodorum. ARC Discovery $235,000 AUD.
• Solomon, P.S., Oliver, R.P. and Lipscombe, R.J. (2008) Proteome mapping of the model fungal plant pathogen Stagonospora nodorum using LC-LC-MS/MS. ARC Linkage $78,000 AUD.