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Fungal foes forge ahead

Posted by: HelenFones

Zymoseptoria tritici, causal agent of leaf blotch disease, growing across a wheat leaf surface in the early stages of infection. SEM by Dr H Fones, University of Exeter
Zymoseptoria tritici, causal agent of leaf blotch disease, growing across a wheat leaf surface in the early stages of infection. SEM by Dr H Fones, University of Exeter

People are strange...

A striking example of that strangeness can be seen in the way we create and relate to monsters.  Horror as a genre has longstanding appeal: from the monsters of mythology through Stoker’s Dracula to the modern horror movie, our enjoyment of the chilling endures.  At the same time, we have a startling ability to ignore the chilling in the everyday world. 

There are multifarious monsters all around.  Consider emerging infectious diseases (EIDs)1, all but invisible except to specialists (and victims!), despite brief moments in the headlines: Bats dying!2 Fungus driving frogs extinct!3 Colony collapse threatens bees!4.  Such threats to charismatic fauna concern us; we even treasure charismatic flora, as the response to ash dieback showed.  But what if monsters threaten something more ordinary?  Like… bread?

What if monsters threaten something ordinary? 

‘Mundane monsters’ might describe these threats, which undermine our food security, but rarely capture public imagination.  After all, I wouldn’t call wheat charismatic: it looks like grass, and has the habit of falling over when taken from its cosy growth cabinet: a spineless sissy of a staple crop.  But staple it is.  And threatened, too.  EIDs decimate yields – a recently discovered strain (Ug99) of wheat stem rust can cause 100% crop losses1.  Discovered in Uganda in 19905, Ug99 reached Iran in 20076 and is a threat to wheat worldwide5.

Rust fungi are particularly monstrous, because they survive in intercontinental air currents.  But other EIDs also travel: transport and trade make their spread unstoppable.  At Exeter, Dan Bebber and Sarah Gurr have determined that with climate change, mundane monsters are marching polewards at 3 km a year7 and can be expected to saturate important agricultural countries by 2050, with fungi spreading fastest8.  If that isn’t scary enough, then note this: like all good monsters, crop diseases are stealthy.  Dan calculates that, with sufficient investment, an average of 200 additional crop pests and diseases per nation could be uncovered9.  Even when we are aware of these threats, we don’t understand them well: the wheat pathogen Zymoseptoria tritici, which destroys up to 1.5 billion euros worth of wheat every year just in the UK, France and Germany10, is obscure in many ways11, although work at Exeter in the Gurr and Steinberg labs seeks to help elucidate its interactions with wheat12 and its basic cell biology13.

The mundane monsters are coming.  They’re stealthy; they’re already here.  And they are stealing your dinner.  Maybe ‘mundane’ is misleading.

 

Citations

1 - Fisher, Matthew C., et al. "Emerging fungal threats to animal, plant and ecosystem health." Nature 484.7393 (2012): 186-194.  http://rdcu.be/ehl7  or http://www.nature.com/nature/journal/v484/n7393/full/nature10947.html

2 - Farrer, Rhys A., et al. "Multiple emergences of genetically diverse amphibian-infecting chytrids include a globalized hypervirulent recombinant lineage." Proceedings of the National Academy of Sciences 108.46 (2011): 18732-18736.

http://www.pnas.org/content/108/46/18732.full

3 - Wibbelt, G. et al. White-nose syndrome Fungus (Geomyces destructans) in Bats, Europe. Emerg. Infect. Dis. 16, 1237–1243 (2010)  http://wwwnc.cdc.gov/eid/article/16/8/10-0002_article

4 - Cameron, S. A. et al. Patterns of widespread decline in North American bumble bees. Proc. Natl Acad. Sci. USA 108, 662–667 (2011) http://www.pnas.org/content/108/2/662.full

5 - Singh, Ravi P., et al. "The emergence of Ug99 races of the stem rust fungus is a threat to world wheat production." Annual review of phytopathology 49 (2011): 465-481.  http://www.annualreviews.org/doi/full/10.1146/annurev-phyto-072910-095423?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed

6 - Nazari, K., et al. "Detection of wheat stem rust (Puccinia graminis f. sp. tritici) race TTKSK (Ug99) in Iran." Plant Disease 93.3 (2009): 317-317.  http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-93-3-0317B

7 - Bebber, Daniel P., Mark AT Ramotowski, and Sarah J. Gurr. "Crop pests and pathogens move polewards in a warming world." Nature climate change 3.11 (2013): 985-988.  http://www.nature.com/nclimate/journal/v3/n11/full/nclimate1990.html

8 - Bebber, Daniel P., Timothy Holmes, and Sarah J. Gurr. "The global spread of crop pests and pathogens." Global Ecology and Biogeography 23.12 (2014): 1398-1407.  http://onlinelibrary.wiley.com/doi/10.1111/geb.12214/abstract

9 - Bebber, Daniel P., et al. "Economic and physical determinants of the global distributions of crop pests and pathogens." New Phytologist 202.3 (2014): 901-910. http://onlinelibrary.wiley.com/doi/10.1111/nph.12722/abstract

10 - Fones, Helen, and Sarah Gurr. "The impact of Septoria tritici Blotch disease on wheat: an EU perspective." Fungal Genetics and Biology 79 (2015): 3-7. http://www.sciencedirect.com/science/article/pii/S1087184515000705

11 - Sánchez-Vallet, Andrea, et al. "Is Zymoseptoria tritici a hemibiotroph?." Fungal Genetics and Biology 79 (2015): 29-32.

http://www.sciencedirect.com/science/article/pii/S1087184515000584

12 - Fones, Helen N., Gero Steinberg, and Sarah Jane Gurr. "Measurement of virulence in Zymoseptoria tritici through low inoculum-density assays." Fungal Genetics and Biology 79 (2015): 89-93. http://www.sciencedirect.com/science/article/pii/S1087184515000638

13 - Steinberg, Gero. "Cell biology of Zymoseptoria tritici: Pathogen cell organization and wheat infection." Fungal Genetics and Biology 79 (2015): 17-23.   http://www.sciencedirect.com/science/article/pii/S108718451500064X

Zymoseptoria tritici (green) grows between the cells and fills the substomatal spaces of a wheat leaf (red) with spore-producing structures.

Zymoseptoria tritici (green) grows between the cells and fills the substomatal spaces of a wheat leaf (red) with spore-producing structures.

 

By Dr Helen Fones, Associate Research Fellow at the Unviersity of Exeter. 

@quietscientist

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