tag:theconversation.com,2011:/id/topics/fungal-pathogen-24093/articlesFungal pathogen – The Conversation2023-02-16T19:05:16Ztag:theconversation.com,2011:article/1995932023-02-16T19:05:16Z2023-02-16T19:05:16ZBefore The Last of Us, I was part of an international team to chart the threat of killer fungi. This is what we found<figure><img src="https://images.theconversation.com/files/510490/original/file-20230216-26-fl8d1b.jpg?ixlib=rb-1.1.0&rect=2%2C0%2C1579%2C1055&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://pressroom.warnermedia.com/us/image/tlu106120221lh0106">Liane Hentscher/HBO</a></span></figcaption></figure><p>Fungal infections have received a frenzy of attention thanks to the popularity of HBO’s <a href="https://www.hbo.com/the-last-of-us">The Last of Us</a>. The show depicts a fungal pandemic caused by the real-life zombie-ant fungus, <em><a href="https://www.nationalgeographic.com/animals/article/cordyceps-zombie-fungus-takes-over-ants">Ophiocordyceps unilateralis</a></em>. It imagines the outcome of society’s collapse and a brutal approach to maintaining public health.</p>
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<p>But in (real-life) laboratories, hospitals and public health units around the world, researchers have been warning about the rise of potentially deadly fungal infections for years. </p>
<p>With few drugs to treat major fungal infections, and no vaccines on the horizon, the potential harm caused by fungal infections have raised alarms at the highest levels of public health. </p>
<p>I was part of a large international team of researchers commissioned by the <a href="https://www.who.int/publications/i/item/9789240060241">World Health Organization</a> (WHO) to understand which fungal pathogens we most needed to research and which posed the greatest public health threat. This is what its report found. </p>
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<strong>
Read more:
<a href="https://theconversation.com/the-last-of-us-fungal-infections-really-can-kill-and-theyre-getting-more-dangerous-198184">The Last of Us: fungal infections really can kill – and they’re getting more dangerous</a>
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<h2>Fungi back in the spotlight</h2>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/uLtkt8BonwM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Last of Us reminds us how deadly some fungi can be.</span></figcaption>
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<p>Before The Last of Us, many people thought “fungus” meant mushrooms or something mouldy in the compost heap. If they thought of fungi in relation to health, they thought of <a href="https://www.cdc.gov/healthywater/hygiene/disease/athletes_foot.html">athlete’s foot</a> or <a href="https://theconversation.com/explainer-why-do-we-get-fungal-nail-infections-and-how-can-we-treat-them-75212">toenail infections</a> – familiar, but not frightening. </p>
<p>However, fungi do cause serious infections, especially in people with other health conditions. People living with cancer, HIV, or diabetes are especially at risk of these infections, but they can also strike those who have had major surgery, ended up in an intensive care unit, or who have experienced another serious infection. This is because their immune system is weakened or distracted, opening up a space for “opportunistic infections”.</p>
<p>We’ve seen this in India where black mould infections (<a href="https://theconversation.com/what-is-mucormycosis-the-fungal-infection-affecting-covid-patients-in-india-160707">mucormycosis</a>) complicated cases of COVID, resulting in <a href="https://www.bbc.com/news/world-asia-india-57897682">thousands of deaths</a>.</p>
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Read more:
<a href="https://theconversation.com/what-is-mucormycosis-the-fungal-infection-affecting-covid-patients-in-india-160707">What is mucormycosis, the fungal infection affecting COVID patients in India?</a>
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<h2>A threat and becoming more so</h2>
<p>Well before The Last of Us, health authorities had been starting to take notice of serious fungal infections.</p>
<p>In 2019 the US Centers for Disease Control <a href="https://www.cdc.gov/drugresistance/biggest-threats.html">designated</a> the deadly yeast <em><a href="https://theconversation.com/explainer-what-is-candida-auris-and-who-is-at-risk-115293">Candida auris</a></em> – which appeared out of nowhere <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1348-0421.2008.00083.x">in 2009</a> – as an “<a href="https://www.nytimes.com/2019/04/06/health/drug-resistant-candida-auris.html">urgent threat</a>” because of its resistance to many (and sometimes all) known antifungal drugs.</p>
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<a href="https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Candida auras" src="https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510271/original/file-20230215-1870-uc209n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"><em>Candida auris</em> is an ‘urgent threat’ as it’s resistant to most antifungal drugs.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/candida-auris-fungi-emerging-multidrug-resistant-1164101620">Kateryna Kon/Shutterstock</a></span>
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<p>
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Read more:
<a href="https://theconversation.com/explainer-what-is-candida-auris-and-who-is-at-risk-115293">Explainer: what is Candida auris and who is at risk?</a>
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<p>A drug-resistant strain of <em>Aspergillus fumigatus</em>, which arose from <a href="https://www.theatlantic.com/science/archive/2018/11/when-tulips-kill/574489/">overuse of antifungal chemicals</a> in agriculture, made the “watch” list.</p>
<p>New and increasingly drug-resistant pathogens like these are one challenge to public health. Another is the increasing number of people at risk of these infections. </p>
<p>Rich countries are delivering ever-more sophisticated health care, resulting in more people vulnerable to serious fungal infections. Chemotherapy, organ transplants, major surgery, extra healthy years lived with diabetes all give opportunities for fungi to take hold. </p>
<p>Although the risk factors in lower income settings are different, the numbers tell the same story – rates of serious fungal infections <a href="https://www.nbcnews.com/health/health-news/fungal-infections-more-common-as-ranges-expand-rcna58258">globally</a> <a href="https://www.sciencedirect.com/science/article/pii/S0740257019300425?via%3Dihub">are rising</a>.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-cdc-warns-antibiotic-resistant-fungal-infections-are-an-urgent-health-threat-127095">Why the CDC warns antibiotic-resistant fungal infections are an urgent health threat</a>
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<h2>Then we worked with the WHO</h2>
<p>I was part of a large team of international researchers commissioned by the WHO to analyse the past ten years of research on fungal pathogens.</p>
<p>We conducted a worldwide survey of fungal disease experts to understand which pathogens were most in need of research and which posed the greatest public health threat. The WHO <a href="https://www.who.int/publications/i/item/9789240060241">published the results</a> in a report released last year.</p>
<p>They highlighted four critical priority pathogens: </p>
<ul>
<li><p><em>Candida auris</em>, which is resistant to most antifungals and is a problem for vulnerable patients in hospitals</p></li>
<li><p><em>Aspergillus fumigatus</em>, which mainly affects the lungs. Infections can be deadly, even more so when drug-resistant strains are involved </p></li>
<li><p><em>Candida albicans</em>, which can cause invasive infections, typically in vulnerable patients</p></li>
<li><p><em>Cryptococcus neoformans</em>, which can infect the brain, especially in immunocompromised people. This is especially the case in people with HIV, where it’s a leading killer.</p></li>
</ul>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Aspergillus fumigatus" src="https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510272/original/file-20230215-3916-slyox6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"><em>Aspergillus fumigatus</em> mainly affects the lungs.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/fungi-aspergillus-black-mold-that-produce-2128528781">Kateryna Kon/Shutterstock</a></span>
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<p>The WHO report calls for enhanced surveillance, a focus on research and development, and improvements in public health interventions, such as improved prophylaxis (preventive treatments) or infection prevention strategies.</p>
<p>Viewers of The Last of Us will understand why these are so important. We need surveillance so we know where threats are coming from before they arrive, otherwise we cannot prepare.</p>
<p>We need more research and development to develop vaccines and new treatments.</p>
<p>So far, we have failed to develop any <a href="https://www.nature.com/articles/s41541-021-00294-8">anti-fungal vaccines</a> and there is no chance we could produce and distribute one as we did for COVID.</p>
<p>Although some new anti-fungals have become available, the range is still too small, and some strains of fungi are resistant to all available drugs.</p>
<p>Developing vaccines and drugs is hard because fungal cells are similar to human ones. So basic laboratory research is vital to identify ways we can kill fungal cells without harming our own.</p>
<p>Without giving any spoilers, it’s safe to say the public health interventions in The Last of Us are pretty extreme. So research on how to contain and control fungal pathogens is also vital to avoid such draconian and ineffective measures.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-are-zombies-real-79347">Curious Kids: Are zombies real?</a>
</strong>
</em>
</p>
<hr>
<h2>Are fungal pandemics possible?</h2>
<p>The fungal frog plague, <a href="https://theconversation.com/deadly-frog-fungus-has-wiped-out-90-species-and-threatens-hundreds-more-113846">chytrid disease</a>, has killed countless amphibians. Researchers say it has caused the <a href="https://www.science.org/doi/10.1126/science.aav0379">greatest loss of biodiversity</a> from a single disease ever recorded. </p>
<p>Is a fungal zombie apocalypse possible? Not for humans. The fungus in The Last of Us evolved over millennia to infect a specific ant species and influence its behaviour. There is no realistic prospect of this organism crossing over into humans and controlling us. </p>
<p>However, we do face very real threats from fungi if we don’t work hard to understand them better – threats to our health, to biodiversity, even food security. By taking action now, we can prevent a potential public health crisis.</p><img src="https://counter.theconversation.com/content/199593/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Justin Beardsley receives funding from the NHMRC and has received honoraria from Gilead for hosting education meetings. He was part of a WHO-commissioned study group, but any views expressed here are his alone and do not represent the official views of the WHO. </span></em></p>Dangerous fungal infections are on the rise globally. But we have few drugs that work and no prospect of anti-fungal vaccines any time soon.Justin Beardsley, Associate Professor in Infectious Diseases, Sydney Institute for Infectious Diseases Westmead Clinical School, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1291862020-01-20T04:34:02Z2020-01-20T04:34:02ZAustralia’s threatened bats need protection from a silent killer: white-nose syndrome<figure><img src="https://images.theconversation.com/files/308196/original/file-20191223-11891-zcp8mn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Three North American little brown bats with signs of white-nose syndrome, which is virtually certain to hit Australian bats without further action.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/usfwshq/5614360878">KDFWR/Terry Derting</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>We already know how deadly this summer’s fires have been for <a href="https://theconversation.com/six-million-hectares-of-threatened-species-habitat-up-in-smoke-129438">mammals, birds, and reptiles</a> across Australia. But beyond this bushfire season, many of those same species – including our <a href="http://ausbats.org.au/about-bats/4551313477">bats</a>, which make up around a quarter of all Australian mammal species – are facing another devastating threat to their survival.</p>
<p><a href="https://www.whitenosesyndrome.org/">White‐nose syndrome</a> has recently decimated bat populations across North America. While the fungal pathogen responsible for this disease, <em>Pseudogymnoascus destructans</em>, <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0204282">currently doesn’t occur</a> in Australia, the fungus is <a href="https://www.publish.csiro.au/WR/justaccepted/WR18194">virtually certain</a> to jump continents in the next decade.</p>
<p>Our recent research, published in the journal <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/aec.12832?af=R">Austral Ecology</a>, attempted to quantify this risk – and the results are not encouraging. Up to eight bat species occupy caves in south-eastern Australia that provide conditions suitable for the fungus to grow. </p>
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<img alt="" src="https://images.theconversation.com/files/309171/original/file-20200108-138649-1c2pb1q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/309171/original/file-20200108-138649-1c2pb1q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=463&fit=crop&dpr=1 600w, https://images.theconversation.com/files/309171/original/file-20200108-138649-1c2pb1q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=463&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/309171/original/file-20200108-138649-1c2pb1q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=463&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/309171/original/file-20200108-138649-1c2pb1q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=582&fit=crop&dpr=1 754w, https://images.theconversation.com/files/309171/original/file-20200108-138649-1c2pb1q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=582&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/309171/original/file-20200108-138649-1c2pb1q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=582&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Large parts of southern Australia provides cave habitat suitable for growth by the cold-loving fungus responsible for white-nose syndrome.</span>
<span class="attribution"><span class="source">Turbill & Welbergen 2019</span></span>
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</figure>
<p>Even before this summer’s fires, seven of those types of bats were listed on state or federal legislation as threatened with extinction. This includes the <a href="http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=87645">critically endangered</a> southern bent-winged bat (<em>Miniopterus orianae bassanii</em>), a species whose caves would all provide optimal conditions for growth of the fungus.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/308066/original/file-20191220-11919-1txtlq4.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/308066/original/file-20191220-11919-1txtlq4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308066/original/file-20191220-11919-1txtlq4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308066/original/file-20191220-11919-1txtlq4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308066/original/file-20191220-11919-1txtlq4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308066/original/file-20191220-11919-1txtlq4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308066/original/file-20191220-11919-1txtlq4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">All caves occupied by the critically endangered southern bent-winged bat provide ideal thermal conditions for white-nose syndrome.</span>
<span class="attribution"><span class="source">Dr Lindy Lumsden</span></span>
</figcaption>
</figure>
<h2>Millions of bats wiped out in North America</h2>
<p><a href="https://www.whitenosesyndrome.org/">White-nose syndrome</a> was first detected in the United States in 2006 at a popular tourist cave in the state of New York. Since then, the disease has <a href="https://www.whitenosesyndrome.org/spreadmap">spread</a> across North America, killing millions of bats in its wake, with many local populations experiencing 90 to 100% mortality.</p>
<p>The <a href="https://www.pnas.org/content/109/18/6999">novel pathogen hypothesis</a> explains why <em>P. destructans</em> has such catastrophic impacts on North American bats: the immune system of these species is evolutionarily naive to this fungal attack. Accordingly, in Europe and Asia, where <em>P. destructans</em> is endemic and widespread, few bats exhibit white‐nose syndrome and mortalities are rare. </p>
<p>Australia’s unique wildlife is inherently at risk from invasive novel pathogens because of its long‐term biogeographical isolation. Thus Australian bats, like their distant North American relatives, probably lack an effective immune response to <em>P. destructans</em> and would be susceptible to developing white-nose syndrome.</p>
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<a href="https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=342&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=342&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=342&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=429&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=429&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308073/original/file-20191220-11946-1ju7j66.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=429&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Since its detection in the United States in 2006, white-nose syndrome has received extensive media attention globally.</span>
</figcaption>
</figure>
<h2>Hibernation is the key risk period</h2>
<p>Most fungal pathogens grow best at cool temperatures, and a high body temperature in mammals and birds provides an <a href="https://academic.oup.com/jid/article/200/10/1623/881601">effective barrier</a> against fungal diseases. The fungus causing white-nose syndrome is also cold-loving, ceasing to grow at temperatures above 20°C. The only time it can infect and kill bats is when they hibernate. </p>
<p>Bats go cold (use <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12137">torpor</a>) during hibernation to prevent starvation over winter in temperate climates. Hibernating bats that are infected by <em>P. destructans</em> rewarm more frequently than normal. These unscheduled bursts of metabolic heat production prematurely burn up the body fat of overwintering bats. Hence, despite the damage caused by white-nose syndrome to the bat’s skin tissue, they apparently die due to starvation or dehydration.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/308068/original/file-20191220-11929-10yg6bx.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/308068/original/file-20191220-11929-10yg6bx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308068/original/file-20191220-11929-10yg6bx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308068/original/file-20191220-11929-10yg6bx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308068/original/file-20191220-11929-10yg6bx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=525&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308068/original/file-20191220-11929-10yg6bx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=525&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308068/original/file-20191220-11929-10yg6bx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=525&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The infection is easily visible under UV light.</span>
<span class="attribution"><span class="source">Turner et al. 2014</span></span>
</figcaption>
</figure>
<p>Hibernation is key to predicting the susceptibility of bat populations to mortality from white-nose syndrome: those with less energy to spare over winter are more at risk. Consequently, white-nose syndrome has fuelled a large research program on the winter ecology and hibernation physiology of North American bats.</p>
<p>Bats in south-eastern Australia do enter a period of winter hibernation, but that is about the extent of what we know. This knowledge gap makes it impossible to predict how they will respond if exposed to <em>P. destructans</em>. Even non-lethal impacts, however, will worsen the extinction-bound trajectory of several cave-roosting species, most notably the eastern and southern bent-winged bats.</p>
<h2>What can Australia do?</h2>
<p>Given the impending arrival of <em>P. destructans</em> in Australia, and our study’s findings of widespread thermal cave suitability in south-eastern Australia, we urge immediate action. This includes tightening biosecurity measures and gaining missing information on bat biology so we are better prepared for a possible white-nose syndrome epidemic.</p>
<p>The importance of this threat has not been missed by Wildlife Health Australia, which has produced <a href="https://www.wildlifehealthaustralia.com.au/ProgramsProjects/BatHealthFocusGroup.aspx#WNS">guidelines</a> for reporting and response to incursion. Advice is also available from the <a href="https://www.agriculture.gov.au/pests-diseases-weeds/animal/white-nose-syndrome">Commonwealth</a>. Just recently, white-nose syndrome was listed in the <a href="https://www.agriculture.gov.au/biosecurity/environmental/priority-list">national priority list</a> for exotic environmental pests and diseases, ranking in the top five of native animal diseases and their pathogens.</p>
<p><a href="https://www.caves.org.au/conservation">Cave enthusiasts</a> have also been proactive in alerting members to white-nose syndrome and the risk of accidentally introducing <em>P. destructans</em>, especially when returning from overseas caving adventures. And the <a href="http://ausbats.org.au/white-nose-syndrome/4593892491">Australasian Bat Society</a> – a strong advocate for bat conservation – has alerted the public and government agencies to this potential new threat.</p>
<h2>Action now is critical</h2>
<p>At present, there is little that would prevent <em>P. destructans</em> from making it its way to Australian caves, despite two years passing since experts assessed the risk of incursion as almost certain.</p>
<p>We need effective measures at all levels, from requiring incoming visitors to identify contact with cave environments, to decontamination procedures at caves popular with international tourists.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=924&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=924&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=924&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1161&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1161&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308078/original/file-20191220-11900-mrhalt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1161&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The US Fish and Wildlife Service’s White-nose Syndrome Response Team produced this infographic, including what you can do to help bats.</span>
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<p>Predicting the impact of white-nose syndrome on Australian bats is currently not possible because we know so little about their winter biology. We urge the Australian government to fund specific research to gain this information.</p>
<p>The US Fish and Wildlife Service has injected more than US$46 million since 2008 into <a href="https://www.whitenosesyndrome.org/funding-projects">research</a> and fieldwork to address the threat. Australian researchers can use this work to focus on the critical data needed to inform <a href="https://advances.sciencemag.org/content/2/1/e1500831">models</a> that predict the vulnerability of local bat populations.</p>
<h2>Why we need bats to survive</h2>
<p>Bats are incredibly <a href="https://theconversation.com/why-we-shouldnt-be-so-quick-to-demonise-bats-87693">valuable</a> in their own right. But the world needs healthy bat populations: a single insectivorous bat can eat up to half its body mass in insects each night, and together colonies of bats provide a service with an <a href="https://science.sciencemag.org/content/332/6025/41">estimated value</a> to the agricultural industry alone in the billions of dollars per year. </p>
<p>We hope this terrible disease will not threaten Australian bats. But the precautionary principle dictates we should plan and act now, assuming the worst-case scenario. Alarm bells are ringing.</p>
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<p><a href="https://theconversation.com/why-we-shouldnt-be-so-quick-to-demonise-bats-87693">Read more: The importance of Australia’s weird and wonderful bats</a></p>
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<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/308072/original/file-20191220-11939-b98v4o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308072/original/file-20191220-11939-b98v4o.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=334&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308072/original/file-20191220-11939-b98v4o.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=334&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308072/original/file-20191220-11939-b98v4o.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=334&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308072/original/file-20191220-11939-b98v4o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308072/original/file-20191220-11939-b98v4o.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308072/original/file-20191220-11939-b98v4o.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A selection of Australia’s bat diversity. Top row from left: grey-headed flying-fox; orange leaf-nosed bat; common blossom bat; large-footed myotis. Bottom row: golden-tipped bat; eastern horseshoe bat; common sheath-tailed bat; ghost bat.</span>
<span class="attribution"><span class="source">Justin Welbergen (grey-headed flying-fox, eastern horseshoe bat); Nicola Hanrahan (ghost bat); Bruce Thomson (golden-tipped bat); Steve Parish & Les Hall for remainder of species</span></span>
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</figure><img src="https://counter.theconversation.com/content/129186/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Turbill receives funding from the Australian Research Council (ARC). </span></em></p><p class="fine-print"><em><span>Justin Welbergen receives funding from the Australian Research Council (ARC)</span></em></p>It’s been a deadly summer for Australia’s wildlife. But beyond the fires, we need to act now to protect bats – which make up a quarter of Australian mammal species – from a silent overseas killer.Christopher Turbill, Senior Lecturer in Animal Ecology, Western Sydney UniversityJustin A. Welbergen, President of the Australasian Bat Society | Associate Professor of Animal Ecology, Western Sydney UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/945762018-04-08T19:49:11Z2018-04-08T19:49:11ZWhy Australia imports so many veggie seeds (and do we really need to treat them with fungicides?)<figure><img src="https://images.theconversation.com/files/213538/original/file-20180406-125167-y4dih6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Australian growers Imported rassicaceae seeds, including radishes, may be required o </span> </figcaption></figure><p>Organic farmers have <a href="https://www.smh.com.au/politics/federal/organics-industry-shocked-by-official-plan-for-forced-chemical-sprays-20180330-p4z714.html">reacted with alarm</a> to a <a href="http://www.agriculture.gov.au/biosecurity/risk-analysis/plant/brassicaceous-crop-seeds">draft review</a> released last week that recommends mandatory fungicide treatment for certain plant seeds imported into Australia, including broccoli, cauliflower, radish and spinach. </p>
<p>Over 19,000 people have signed a <a href="https://www.change.org/p/minister-for-agriculture-and-water-resources-david-littleproud-mp-protect-our-organic-vegetable-seed-supply-from-mandatory-fungicide-treatment?recruiter=30292772&utm_source=share_petition&utm_medium=copylink&utm_campaign=share_petition">change.org</a> petition objecting to the proposal, which is designed to strengthen biosecurity for plants of the brassicaceae family. Opponents say mandatory fungicide treatment could spell the loss of organic accreditation for organic vegetable growers who rely on imported seed.</p>
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Read more:
<a href="https://theconversation.com/explainer-why-australia-needs-biosecurity-20105">Explainer: why Australia needs biosecurity</a>
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<h2>Why do we need to import seeds?</h2>
<p>Australia’s vegetable growers do rely heavily on imported seed. But why?</p>
<p>The answer lies partly in where plant breeding expertise and effort is centred globally. Continuous (and often long-term) efforts in breeding have lead to the development of plant varieties with benefits like improved yield or quality, tolerance to stress and resistance to disease. These varieties have major advantages for growers (provided they are suitable for Australian conditions).</p>
<p>The global vegetable seed market is dominated by a small number of multinational companies. These international companies produce seeds in multiple locations around the world to reduce the risk of running low on popular varieties, and to benefit from the counter seasons of the northern and southern hemispheres.</p>
<p>However, seed grading, testing and treatment (including fungicide coating) is generally centrally coordinated at the company’s key global facility. These facilities are typically in close proximity to major vegetable growing regions, and thus outside Australia.</p>
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<strong>
Read more:
<a href="https://theconversation.com/dont-believe-everything-you-hear-about-pesticides-on-fruits-and-vegetables-74140">Don't believe everything you hear about pesticides on fruits and vegetables</a>
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<p>There are several companies distributing or producing vegetable seed in Australia, however most are owned by foreign parent companies and the breeding is done by them off-shore. In this case, subsidiary groups in Australia import the seed from the parent company, grow a crop for seed, and then may sell locally or return the seed to the parent company for quality control and global sale and distribution.</p>
<p>If seed were grown in Australia only for a domestic market, it would be a very small market without the benefits of an economy of scale. However, there are other benefits of breeding and growing crops for vegetable seed in Australia, including the scope to prioritise breeding efforts in response to local need. University of Sydney-based company Abundant Produce is addressing this gap for some vegetable crops, but not any brassicas as yet.</p>
<h2>Can we protect biosecurity and organic farmers at the same time?</h2>
<p>To address the dilemma faced by organic brassica growers who rely on imported seed, can the risk of diseases entering Australia be managed in organically acceptable ways?</p>
<p>In their draft review of the risk analysis for import of brassica seeds, the Department of Agriculture and Water Resources do clearly state that alternative measures will be considered if the “appropriate level of protection” can be achieved.</p>
<p>These alternatives may include importing seed from areas or production sites that are designated as free of the two pathogens of concern. A further alternative is seeds that have been grown using at least two independent and verified disease control measures (either pre- or post-harvest) as part of a “<a href="https://www.ippc.int/en/publications/607/">systems approach</a>” to manage pest risk.</p>
<p><a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.687.5969&rep=rep1&type=pdf">Non-fungicide seed treatments</a> could also be considered. Heat, applied via steam, water or air, <a href="https://apsjournals.apsnet.org/doi/pdfplus/10.1094/PDIS.2002.86.3.278">electrolysed water</a>, or <a href="http://www.ingentaconnect.com/content/ista/sst/2017/00000045/00000001/art00006">pulsed electric fields</a> could be used, if they achieve the appropriate level of protection and seed viability is maintained. <a href="http://articles.extension.org/pages/18952/organic-seed-treatments-and-coatings#.VaJzTV9Vikp">Organically-approved</a> seed coatings and other treatments may also be an option.</p>
<p>But the efficiency of treatments depends on how the pathogen infects the host and in which <a href="http://www.seedbiology.de/structure.asp">part of the seed</a> it is found. </p>
<p>There are at least eight combinations of <a href="https://www.apsnet.org/publications/phytopathology/backissues/Documents/1983Abstracts/Phyto73_326.htm">seed infection sites and types</a>, and fungal pathogens can use all of these.</p>
<p>One of the fungal pathogens targeted by the proposed regulations is <em><a href="https://dx.doi.org/10.1128%2FgenomeA.00821-16">Colletotrichum higginsianum</a></em> , which infects broccoli, cabbage, kale, cauliflower, bok choy and radishes and causes dark sunken lesions on all above-ground plant parts. </p>
<p>While studies are lacking on how that specific pathogen develops in brasscia seed, <a href="https://scialert.net/abstract/?doi=ijar.2007.812.819">studies with Colletotrichum truncatum in soybean seeds</a> found that it could grow in the cotyledon and embryo but was most abundant in the seed coat.</p>
<p>The other pathogen of concern is a sub-type of <em><a href="https://doi.org/10.1007/BF02981311">Fusarium oxysporum</a></em> which is notorious for vascular wilt diseases in many crops around the world.</p>
<p><em>Fusarium oxysporum f. sp. raphani</em> can cause major crop loss in Eruca vesicaria crops (including rocket) and radishes. These fungal pathgogens can cause systemic infections in the plant, and then <a href="https://www.apsnet.org/publications/phytopathology/backissues/Documents/1983Abstracts/Phyto73_326.htm">establish in the seed</a> as it develops. So, they can be found in any part of the seed, but especially the embryo and seed coat. </p>
<p>The anatomy of the seed itself is also a factor in determining which seed treatment is best. For example, seed of pyrethrum (a daisy from which the household insecticide of the same name is sourced) has a <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ppa.12622">porous coat</a> which makes steaming a commercially viable option for the elimination of <a href="http://ecite.utas.edu.au/118260">fungal pathogens</a>. Similarly, <a href="https://apsjournals.apsnet.org/doi/pdf/10.1094/PD-89-1305">heat treatments and chlorine</a> are used to disinfect spinach seed.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/you-say-tomato-why-some-fruits-are-forever-doomed-to-be-called-veggies-62099">You say tomato... why some fruits are forever doomed to be called veggies</a>
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<p>Another advantage of finding alternatives to fungicide treatment of imported seed is that frequent use of fungicides can lead to pathogen <a href="http://www.frac.info/resistance-overview/mechanisms-of-fungicide-resistance">resistance</a>. This means that the pathogens evolve to overcome its mode of action and are no longer controlled by it. </p>
<p>Broad-spectrum fungicides have been recommended by the Department of Agriculture and Water Resources for mandatory seed treatment, and the selection and management of these as part of resistance risk assessment requires attention by all growers. </p>
<p>It should be possible to satisfy both biosecurity stringency and the organic vegetable sector if enough time and resources are given to finding solutions. Establishing local breeding and seed production efforts would take a solid business case and investment. Assessment of seed treatment alternatives would require research trials and require cooperation from seed companies. </p>
<p>As always, the question is – who is going to pay?</p><img src="https://counter.theconversation.com/content/94576/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karen Barry is the State Councillor for the Australasian Plant Pathology Society, and was previously a director at the Ag Institute Australia. She has received funding from Horticulture Innovation Australia.</span></em></p><p class="fine-print"><em><span>Alistair Gracie receives funding from Hort Innovation Australia and Australian Research Council. He has undertaken research for vegetable seed companies Bejo Seeds, Rijk Zwaan Australia and South Pacific Seeds. </span></em></p><p class="fine-print"><em><span>Jason Scott receives funding from Australian Research Council and Horticulture Innovation Australia Ltd. </span></em></p>A proposal that all imported vegetable seeds be treated with fungicide has drawn outrage from Australia’s organic producers, who fear losing their certification.Karen Barry, Senior Lecturer, Plant Pathology, University of TasmaniaAlistair Gracie, Associate Professor in Horticultural Science, University of TasmaniaJason Scott, Senior Lecturer, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/916982018-02-14T14:24:36Z2018-02-14T14:24:36ZWhite nose syndrome is killing millions of bats via a contagious fungus – here’s how to stop it<figure><img src="https://images.theconversation.com/files/206367/original/file-20180214-174977-lbi6cn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/governmentofalberta/22414730957">Government of Alberta/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>A dangerous fungus has been sweeping across North America with devastating consequences. In the past decade, between 5m and 7m bats in the US and Canada have been wiped out as a result of the fungal disease known as white nose syndrome, which alters their behaviour in potentially deadly ways. But the <a href="https://www.nature.com/articles/s41467-017-02441-z">latest research</a> shows there might be hope for researchers trying to battle the disease, following the discovery that UV light appears to destroy the fungus’s DNA.</p>
<p>White nose syndrome is caused by the fungus <em>Pseudogymnoascus destructans</em>, which grows on the bats’ muzzles (hence the name) and other hairless body parts including wings, and <a href="https://bmcbiol.biomedcentral.com/articles/10.1186/1741-7007-8-135">causes skin lesions</a>. <em>P. destructans</em> is psychrophilic, meaning it thrives in cold temperatures between 4°C and 20°C. This means it affects bats during hibernation.</p>
<p>The itchy, painful lesions cause infected bats to repeatedly wake from hibernation, leaving them confused and causing them to display <a href="http://www.batcon.org/our-work/regions/contact-bci/usa-canada/white-nose-syndrome">highly unusual behavior</a>, such as flying outside during daylight in nearly freezing temperatures. The cold, lack of food and abnormal activity leads to bats depleting their winter fat reserves, and starving, dehydrating or freezing to death. As a result, the disease can kill between <a href="https://www.nature.com/news/2010/100113/full/463144a.html">90% and 100%</a> of bats in affected hibernating colonies.</p>
<p>Out of the 47 bat species native to the US and Canada, over half rely on hibernation for survival. <a href="https://www.whitenosesyndrome.org/about/bats-affected-wns">Nine of these species</a> (including two endangered and one threatened) already show symptoms of white nose syndrome. <em>P. destructans</em> has also been found in another six species (including one endangered) that don’t yet show symptoms. The little brown bat (<em>Myotis lucifugus</em>), once the most common bat in North America, is now predicted to face <a href="http://science.sciencemag.org/content/329/5992/679">regional extinction</a>.</p>
<p>Bats normally live a long time and produce only a single pup each year, so affected species are unlikely to recover quickly. Not only is this bad for biodiversity, but it could also have a serious economic impact on humans. In temperate regions, bats eat up to 600 insects a night and so provide a vital pest-control service for North American farmers, effectively worth <a href="http://science.sciencemag.org/content/332/6025/41">US$3.7 billion a year</a>.</p>
<h2>How did this bat-astrophe come about?</h2>
<p><em>P. destructans</em> has probably co-existed with bats in Eurasia for <a href="https://www.nature.com/articles/s41467-017-02441-z">millions of years</a>. As a result, these bats have evolved defences against the fungus. So in this part of the world, despite the occasional mild outbreak of white nose syndrome, the disease <a href="http://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(11)00192-3">doesn’t significantly impact entire groups of bats</a>. But when <em>P. destructans</em> was introduced to the previously unexposed American bats, the effects were disastrous.</p>
<p>White nose syndrome was discovered in North America <a href="http://science.sciencemag.org/content/323/5911/227">in 2006</a>. We know that the fungus was most likely spread by human activity because the North American fungus is <a href="https://www.sciencedirect.com/science/article/pii/S0960982215000792">almost genetically identical</a> to some of the samples found in Europe. Also, bats don’t migrate between the two continents and some of the distances between contaminated caves in the US are longer than the flying range of affected bats. On top of that, the first reports of white nose syndrome came from a <a href="https://wwwnc.cdc.gov/eid/article/16/8/10-0002_article">popular tourist cave near Albany, New York</a>. So the fungus probably spread via contaminated clothing and caving equipment from tourists visiting affected areas.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/206369/original/file-20180214-175001-nyeuec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/206369/original/file-20180214-175001-nyeuec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/206369/original/file-20180214-175001-nyeuec.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/206369/original/file-20180214-175001-nyeuec.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/206369/original/file-20180214-175001-nyeuec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/206369/original/file-20180214-175001-nyeuec.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/206369/original/file-20180214-175001-nyeuec.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Checking for white nose syndrome.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/wildlife-biologist-checking-wings-big-brown-797424433">Shutterstock</a></span>
</figcaption>
</figure>
<p>Since then, white nose syndrome has become one of the most severe wildlife diseases ever recorded. Yet there may literally be a light at the end of the tunnel. A <a href="https://www.nature.com/articles/s41467-017-02441-z">research team from the US Forest Service</a> has discovered that <em>P. destructans</em> is extremely sensitive to ultra-violet light, particularly to UV-C light that kills germs but doesn’t cause skin cancer. They found that moderate doses of UV-C light killed over 99% of the fungus, and that even low doses killed 85%.</p>
<p>The effect is so potent because UV light destroys the fungus’s DNA, and, unlike <a href="https://bmcgenomics.biomedcentral.com/articles/10.1186/1471-2164-15-6">related fungi</a>, <em>P. destructans</em> can’t repair the damage. Further tests are on the way to check whether UV light causes any damage to the bats themselves. But the fact that UV-C light has already been used in treatments of <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2133.2008.08549.x/abstract;jsessionid=DACFFB496B5103A02CDAC89BD89CB96F.f01t02">other fungal infections</a> in mammals means the discovery is very promising.</p>
<p>Managing wildlife diseases can be difficult and expensive. Think of how hard it would be to apply fungicide skin cream to tens of thousands of bats hanging from the top of a cave. But shining a simple hand-held UV-C light source on them would be much easier. So this research could have huge implications for protecting North American bats.</p><img src="https://counter.theconversation.com/content/91698/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joanna M. Bagniewska does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Ultra-violet (UV) light can destroy a fungus that’s devastating the animals in North America.Joanna M. Bagniewska, Teaching Fellow in Zoology and Ecology, University of ReadingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/642062016-10-24T01:59:53Z2016-10-24T01:59:53ZWith the familiar Cavendish banana in danger, can science help it survive?<figure><img src="https://images.theconversation.com/files/142716/original/image-20161021-1763-13xoceb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Facing down a future with no bananas.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/35652152@N07/28004881235">Chris Richmond</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>The banana is the world’s most popular fruit crop, with <a href="http://www.fao.org/economic/worldbananaforum/statistics/en/">over 100 million metric tons produced annually</a> in over 130 <a href="http://www.fao.org/docrep/019/i3627e/i3627e.pdf">tropical and subtropical countries</a>. Edible bananas are the result of a genetic accident in nature that created the seedless fruit we enjoy today. </p>
<p>Virtually all the bananas sold across the Western world belong to the <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0007/251899/Banana-growing-guide-cavendish-bananas-1.pdf">so-called Cavendish subgroup</a> of the species and are <a href="http://doi.org/10.1093/aob/mcm191">genetically nearly identical</a>. These bananas are sterile and <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0006/251898/Banana-growing-guide-cavendish-bananas-Complete.pdf">dependent on propagation via cloning</a>, either by using suckers and cuttings taken from the underground stem or through modern tissue culture.</p>
<p>The familiar bright yellow Cavendish banana is ubiquitous in supermarkets and fruit bowls, but it is in imminent danger. The vast worldwide monoculture of genetically identical plants leaves the Cavendish <a href="http://dx.doi.org/10.1371/journal.ppat.1005197">intensely vulnerable to disease outbreaks</a>. </p>
<p>Fungal diseases severely devastated the banana industry once in history and it could soon happen again if we do not resolve the cause of these problems. Plant scientists, including us, are working out the genetics of wild banana varieties and banana pathogens as we try to prevent a Cavendish crash. </p>
<h2>The cautionary tale of ‘Big Mike’</h2>
<p>One of the most prominent examples of genetic vulnerability comes from the banana itself. Up until the 1960s, Gros Michel, or “Big Mike,” was the prime variety grown in commercial plantations. Big Mike was so popular with consumers in the West that the banana industry established ever larger monocultures of this variety. Thousands of hectares <a href="http://www.apsnet.org/publications/apsnetfeatures/Pages/PanamaDiseasePart1.aspx">of tropical forests</a> in Latin America were converted into <a href="http://www.penguinrandomhouse.com/books/299017/banana-by-dan-koeppel/9780452290082">vast Gros Michel plantations</a>.</p>
<p>But Big Mike’s popularity led to its doom, when a pandemic whipped through these plantations during the 1950s and ‘60’s. A fungal disease called Fusarium wilt or Panama disease nearly wiped out the Gros Michel and brought the global banana export industry to the <a href="http://www.agriculturedefensecoalition.org/sites/default/files/pdfs/3T_2000_Banana_Destructive_Panama_Disease_2000.pdf">brink of collapse</a>. A soilborne pathogen was to blame: The fungus <em>Fusarium oxysporum</em> f.sp. <em>cubense</em> (Foc) <a href="http://dx.doi.org/10.1094/PHYTO-04-15-0101-RVW">infected the plants’ root and vascular system</a>. Unable to transport water and nutrients, the plants wilted and died.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A cross-section of a banana plant, infected with the fungus that causes Fusarium wilt.</span>
<span class="attribution"><span class="source">Gert Kema</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Fusarium wilt is <a href="http://www.promusa.org/Fusarium+wilt">very difficult to control</a> – it spreads easily in soil, water and infected planting material. Fungicide applications in soil or in the plant’s stem are as of yet ineffective. Moreover, the fungus can persist in the soil for several decades, thus prohibiting replanting of susceptible banana plants. </p>
<h2>Is history repeating itself?</h2>
<p>Cavendish bananas are resistant to those devastating Fusarium wilt Race 1 strains, so were able to replace the Gros Michel when it fell to the disease. Despite being less rich in taste and logistical challenges involved with merchandising this fruit to international markets at an acceptable quality, <a href="http://www.apsnet.org/publications/apsnetfeatures/Documents/2005/PanamaDisease2.pdf">Cavendish eventually replaced Gros Michel</a> in commercial banana plantations. The <a href="http://www.fao.org/fileadmin/templates/est/COMM_MARKETS_MONITORING/Bananas/Documents/Banana_Information_Note_2014-_rev.pdf">entire banana industry</a> was restructured, and to date, Cavendish accounts for <a href="http://www.fao.org/docrep/007/y5102e/y5102e04.htm">47 percent of the bananas grown worldwide</a> and <a href="http://www.newyorker.com/magazine/2011/01/10/we-have-no-bananas">99 percent of all bananas sold commercially for export</a> to developed countries. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bananas in Costa Rica affected by Black Sigatoka.</span>
<span class="attribution"><span class="source">Gert Kema</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>But the Cavendish unfortunately has its own weaknesses – most prominently susceptibility to <a href="http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS.2003.87.3.208">a disease called Black Sigatoka</a>. The fungus <em>Pseudocercospora fijiensis</em> attacks the plants’ leaves, causing cell death that affects photosynthesis and leads to a reduction in fruit production and quality. If Black Sigatoka is left uncontrolled, <a href="http://doi.org//10.1111/j.1364-3703.2010.00672.x">banana yields can decline</a> by <a href="http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/BlackSigatoka.aspx">35 to 50 percent</a>.</p>
<p>Cavendish growers currently manage Black Sigatoka through a combination of pruning infected leaves and <a href="http://doi.org/10.17660/ActaHortic.2009.828.16">applying fungicides</a>. Yearly, it can take 50 or more applications of chemicals to control the disease. Such heavy use of fungicides has negative impacts on the environment and the occupational health of the banana workers, and increases the costs of production. It also helps select for survival the strains of the fungus with <a href="http://www.frac.info/working-group/banana-group">higher levels of resistance to these chemicals</a>: As the resistant strains become more prevalent, the disease gets harder to control over time.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=278&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=278&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=278&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=350&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=350&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=350&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Aerial spraying of fungicides on a banana plantation.</span>
<span class="attribution"><span class="source">Gert Kema</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>To further aggravate the situation, Cavendish is also now under attack from <a href="http://dx.doi.org/10.1094/PHYTO-04-15-0101-RVW">a recently emerged strain of Fusarium oxysporum</a>, known as Tropical Race 4 (TR4). First identified in the early 1990s in Taiwan, Malaysia and Indonesia, TR4 has since spread to many Southeast Asian countries and <a href="http://dx.doi.org/10.1094/PDIS-12-14-1356-PDN">on into the Middle East</a> and <a href="http://dx.doi.org/10.1094/PDIS-09-13-0954-PDN">Africa</a>. If TR4 makes it to Latin America and the Caribbean region, the export banana industry in that part of the world could be in big trouble.</p>
<p>Cavendish varieties have shown <a href="http://dx.doi.org/10.1038/504195a">little if any resistance against TR4</a>. Growers are relying on temporary solutions – trying to <a href="http://www.promusa.org/Fusarium+wilt">prevent it</a> from entering new regions, using clean planting materials and limiting the transfer of potentially infected soil between farms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cavendish banana trees in China infected with new fungal disease TR4.</span>
<span class="attribution"><span class="source">Andre Drenth, UQ</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Black Sigatoka and Panama disease both cause serious production losses and are difficult to control. With the right monitoring in place to rapidly intervene and halt their spread, the risks and damage imposed by these diseases can be considerably reduced, as has been <a href="http://www.musalit.org/seeMore.php?id=14394">recently shown in Australia</a>. But current practices don’t provide the durable solution that’s urgently needed.</p>
<h2>Getting started on banana genetic research</h2>
<p>If there’s a lesson to be learned from the sad history of Gros Michel, it’s that reliance on a large and genetically uniform monoculture is a risky strategy that is prone to failure. To reduce the vulnerability to diseases, we need more genetic diversity in our cultivated bananas. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Local banana varieties in southern China.</span>
<span class="attribution"><span class="source">Andre Drenth, UQ</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Over a thousand species of banana have been recorded in the wild. Although most do not have the desired agronomic characteristics – such as high yields of seedless, nonacidic fruits with long shelf life – that would make them a direct substitute for the Cavendish, they are an untapped genetic resource. Scientists could search within them for resistance genes and other desirable traits to use in engineering and breeding programs.</p>
<p>To date, though, there’s been little effort and insufficient funding for collecting, protecting, characterizing and <a href="http://dx.doi.org/10.17660/ActaHortic.2011.897.4">utilizing wild banana genetic material</a>. Consequently, while almost every other crop used for food production has been significantly improved through plant breeding over the last century, the banana industry has yet to benefit from genetics and plant breeding.</p>
<p>But we have started taking the first steps. We now know the <a href="http://dx.doi.org/10.1038/nature11241">genome sequences of the banana</a> and the fungi that <a href="http://dx.doi.org/10.1371/journal.pone.0095543">cause Fusarium wilt</a> and <a href="http://dx.doi.org/10.1371/journal.pgen.1005904">Sigatoka</a>. These studies helped illuminate some of the molecular mechanisms by which these fungal pathogens cause disease in the banana. That knowledge provides a basis for <a href="http://dx.doi.org/10.1371/journal.pgen.1005904">identifying disease-resistant genes</a> in wild and cultivated bananas.</p>
<p>Researchers <a href="http://dx.doi.org/10.1371/journal.pgen.1005876">now have the tools</a> to <a href="https://www.google.co.in/patents/WO2011005090A1?cl=en">identify resistance genes</a> in wild bananas <a href="http://dx.doi.org/10.1073/pnas.1002910107">or other plant species</a>. Then they can use classical plant breeding or genetic engineering to transfer those genes into desired cultivars. Scientists can also use these tools to further study the dynamics and evolution of banana pathogens in the field, and monitor changes in their resistance to fungicides.</p>
<p>Availability of the latest tools and detailed genome sequences, coupled with long-term visionary research in genetics, engineering and plant breeding, can help us keep abreast of the pathogens that are currently menacing the Cavendish banana. Ultimately we need to increase the pool of genetic diversity in cultivated bananas so we’re not dependent on single clones such as the Cavendish or the Gros Michel before it. Otherwise we remain at risk of history repeating itself.</p><img src="https://counter.theconversation.com/content/64206/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>André Drenth receives funding from Horticulture Innovation Australia </span></em></p><p class="fine-print"><em><span>Gert Kema is a senior scientist and professor of tropical phytopathology at Wageningen University and Research. He receives funding for his R&D program on banana, see <a href="http://www.panamadisease.org">www.panamadisease.org</a>. He also co-founded two companies dealing with banana and owns shares in Yellow Pallet, a company that produces transport pallets from banana fiber. </span></em></p><p class="fine-print"><em><span>Ioannis Stergiopoulos does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Every single Cavendish banana plant worldwide is genetically identical. This vast monoculture sets them up for disastrous disease outbreaks. But researchers have ideas on how to protect the crop.Ioannis Stergiopoulos, Assistant Professor of Plant Pathology, University of California, DavisAndré Drenth, Professor of Agriculture and Food Sciences, The University of QueenslandGert Kema, Special Professor of Phytopathology, Wageningen UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/640332016-08-19T10:30:24Z2016-08-19T10:30:24ZHow we’re saving the mountain chicken frog from one of the world’s worst wildlife diseases<figure><img src="https://images.theconversation.com/files/134332/original/image-20160816-13025-hkvuzl.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Mike Hudson</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The mountain chicken frog managed the dubious honour of being at one time both the national dish and a top predator on the Caribbean island of Dominica. Down the centuries <a href="http://www.amphibians.org/froglog/fl032/">overhunting, volcanic eruptions and introduced predators</a> have taken their toll on this, one of the world’s largest frogs. But in recent years the species has been brought to the brink of extinction by a newer, more serious threat described as “<a href="http://www.amphibianark.org/pdf/ACAP_Summit_Declaration.pdf">the worst infectious disease ever recorded among vertebrates</a>”, chytridiomycosis (chytrid).</p>
<p>In susceptible species, the <a href="http://www.amphibianark.org/the-crisis/chytrid-fungus/">chytrid fungus</a> causes thickening of the skin on which many amphibians rely for gas, salt and water absorption. This eventually leads to heart attack and death. While this sounds particularly unpleasant, the most alarming thing about the disease is the speed with which it can drive entire species into decline. You might assume that we have years to prevent the decline of endangered animals as they slowly drift towards extinction. But <a href="http://www.nature.com/articles/srep30772">our research into the mountain chicken frog’s tragic story</a> should serve as a warning about the need to act fast.</p>
<p>Mountain chickens were first observed dying of chytrid on Dominica in 2002. Within 18 months, the disease had driven a <a href="http://www.nature.com/articles/srep30772">population decline of 85%</a>. Despite a number of local campaigns, no wild mountain chickens were seen on the island between 2006 and 2010. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/134474/original/image-20160817-3583-1nq2im1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/134474/original/image-20160817-3583-1nq2im1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134474/original/image-20160817-3583-1nq2im1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134474/original/image-20160817-3583-1nq2im1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134474/original/image-20160817-3583-1nq2im1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134474/original/image-20160817-3583-1nq2im1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134474/original/image-20160817-3583-1nq2im1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Does it taste like chicken too?</span>
<span class="attribution"><span class="source">Daniel Nicholson / ZSL</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Fearing for the future of the species, conservationists’ attention then moved to the only other remaining population of mountain chickens in the world, on
the nearby Caribbean island of Montserrat. Tree frogs that carry the chytrid fungus are known to stow away in regular fruit shipments from Dominica to Montserrat, so it was only a matter of time before the disease arrived in the Montserrat population.</p>
<p>Sure enough, seven years after it was first observed on Dominica, chytrid was observed in Montserrat’s mountain chickens and the population was driven to <a href="http://www.nature.com/articles/srep30772">near extinction within only 18 months</a>. This marks the mountain chicken decline as one of the fastest observed collapses of any species ever recorded.</p>
<p>From the thousands that lived on both islands before the arrival of the disease, there are now thought to be <a href="https://www.theguardian.com/environment/2016/apr/27/monserrats-last-two-mountain-chicken-frogs-to-be-reunited-to-save-species">only two mountain chickens on Montserrat</a> and about <a href="http://www.mountainchicken.org/conservation__trashed/">100 on Dominica</a>. This desperate situation required action.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/134496/original/image-20160817-3602-7c5eey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/134496/original/image-20160817-3602-7c5eey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134496/original/image-20160817-3602-7c5eey.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134496/original/image-20160817-3602-7c5eey.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134496/original/image-20160817-3602-7c5eey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134496/original/image-20160817-3602-7c5eey.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134496/original/image-20160817-3602-7c5eey.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Epidemic victims.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Recovery programme</h2>
<p>Thankfully for the mountain chicken, a group of British and European conservation scientists joined forces with the governments of Dominica and Montserrat to form the <a href="http://www.mountainchicken.org">Mountain Chicken Recovery Programme</a> (MCRP). An eleventh-hour <a href="https://news.mongabay.com/2009/04/after-disease-engulfs-island-rare-mountain-chicken-frogs-airlifted-to-safety/">evacuation of 50 mountain chickens</a> from Montserrat by the MCRP was successful in establishing a captive population in European Zoos. Frogs in these zoos have since successfully bred, ensuring that the species will not go extinct. At least for now.</p>
<p>The MCRP aims to save the mountain chicken from extinction, restoring the species to its historic range and increasing its resilience to future threats. But this is no easy task. The chytrid fungus <a href="http://www.mountainchicken.org/conservation/research/">persists in other amphibian species</a> that appear unaffected and share the forests with the mountain chicken.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/134499/original/image-20160817-3583-rnxbl3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/134499/original/image-20160817-3583-rnxbl3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=953&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134499/original/image-20160817-3583-rnxbl3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=953&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134499/original/image-20160817-3583-rnxbl3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=953&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134499/original/image-20160817-3583-rnxbl3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1197&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134499/original/image-20160817-3583-rnxbl3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1197&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134499/original/image-20160817-3583-rnxbl3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1197&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Repopulating the island.</span>
<span class="attribution"><span class="source">Andrew Cunningham / ZSL</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In order to manage the risk posed by chytrid and conserve the mountain chicken, the MCRP is trialling multiple novel conservation tools. It hopes these measures can not only save the mountain chicken, but also contribute to the conservation of the hundreds of other species impacted by this disease. These measures include the <a href="http://www.sciencedirect.com/science/article/pii/S0006320715302202">world’s first reported use of an anti-fungal drug in the field</a>, following its successful use in captivity.</p>
<p>Several years after the decline, the MCRP also began <a href="https://www.youtube.com/watch?v=T2EckaNA8bU">reintroductions of the mountain chicken to Montserrat</a>, using individuals bred in the European Zoos. Four reintroductions have been carried out so far and analysis is ongoing to measure how successful they have been and how they can be modified to improve their chances of survival.</p>
<p>While these actions are important in preventing species already affected by the disease from going extinct, the most effective protection for other animals would be to stop chytrid spreading in the first place. But even when we are able to predict the arrival of the disease, as on Montserrat, we often have insufficient resources and capacity to stop it.</p>
<p>Without action, amphibian-rich countries such as Sri Lanka – where chytrid is yet to arrive – could suffer a similar fate with catastrophic levels of species loss. If we are to successfully prevent the extinction of further species, we must find ways of developing conservation capacity in those places where amphibians are most at risk.</p><img src="https://counter.theconversation.com/content/64033/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Hudson receives funding from The Balcombe Trust and the Mountain Chicken Recovery Programme has recieved funding from the Darwin Initiative.</span></em></p>A nasty fungus killed 85% of Dominica’s mountain chicken frogs in just 18 months – but the species lives on.Michael Hudson, PhD candidate in biodiversity management, University of KentLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/573202016-05-02T10:07:25Z2016-05-02T10:07:25ZBiologists lose hard-fought ground in race to save bats as white-nose syndrome spreads west<figure><img src="https://images.theconversation.com/files/120062/original/image-20160425-22387-11wfone.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Little brown bat found in western Washington in March 2016. The fungus damaged the bat’s wings, making it unable to fly.</span> <span class="attribution"><a class="source" href="http://wdfw.wa.gov/conservation/health/wns/">Progressive Animal Welfare Society (PAWS)</a></span></figcaption></figure><p>The U.S. Fish and Wildlife Service and the U.S. Geological Survey last month delivered a <a href="https://www.whitenosesyndrome.org/sites/default/files/files/033116_wns_newsrelease_final_dfw.pdf">sobering update</a> on the white-nose syndrome (WNS) epidemic in North America. WNS has been confirmed in a little brown bat (<em>Myotis lucifugus</em>) near North Bend, Washington, over 1,300 miles west of the previously identified western edge of the disease front, Nebraska. </p>
<p>The news hit the WNS and bat conservation community hard. For the previous 10 years, WNS has spread in a stepwise manner from state to state in a radial pattern from Albany, New York, which is thought to be where the infections started. The consistency of this spread allowed researchers to <a href="http://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/6799/MP_CMI_Final.pdf?sequence=1">model the movement of the pathogen</a>, <em>Pseudogymnoascus destructans</em>, with an anticipated arrival on the Pacific Coast in 2026. </p>
<p>Researchers have been developing strategies to control WNS and prevent the massive bat mortalities that have been the hallmark of WNS since 2007. And yet, the disease has spread faster than predicted. Where does this new point of infection leave researchers developing techniques to stall this devastating disease? </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/119881/original/image-20160422-17388-121belo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119881/original/image-20160422-17388-121belo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119881/original/image-20160422-17388-121belo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119881/original/image-20160422-17388-121belo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119881/original/image-20160422-17388-121belo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119881/original/image-20160422-17388-121belo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119881/original/image-20160422-17388-121belo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">WNS spread map.</span>
<span class="attribution"><span class="source">US Fish and Wildlife Service</span></span>
</figcaption>
</figure>
<h2>Gateway to the west</h2>
<p>In order to understand why this is such bad news for bats, one needs to understand how wildlife biologists seek to control the spread of devastating pathogens.</p>
<p>Many of the strategies currently being investigated to minimize the impact of WNS on susceptible bat populations are predicated on the idea that “stop-gap” methods could be employed at geographical choke points to delay the spread of the disease to new populations. That would buy time for scientists to develop permanent solutions, such as vaccinations or “<a href="http://www.ncbi.nlm.nih.gov/probe/docs/applsilencing/">gene silencing</a>” techniques to control the disease.</p>
<p>The arrival of WNS on the West Coast takes this approach off the table in many respects, as it’s already past the geographical bottleneck spots where scientists had hoped to slow it down. But the WNS community has other reasons for concern with this new case. </p>
<h2>“Come here often?”</h2>
<p>Studies of the fungus from the eastern U.S. have shown the pathogen to be mono-clonal. That is, <em>P. destructans</em> in Georgia is the same genetically as <em>P. destructans</em> in Missouri or New York. This is a good thing for bats because it gives them a better chance to develop resistance. </p>
<p>Subsequent evaluation indicates that <em>P. destructans</em>, like most fungi, is likely capable of participating in sexual reproduction in areas where complementary mating types (think male and female, but with numerous potentially compatible “genders”) exist together. When this is considered along with the recent finding that <em>P. destructans</em> and WNS are <a href="http://wwwnc.cdc.gov/eid/article/22/1/15-1314_article">widespread in eastern Asia</a>, it presents the possibility that this West Coast case may have been introduced a new way or it represents a different strain of the fungus. Significantly, it could be a complementary mating type to <em>P. destructans</em> in the eastern U.S. </p>
<p>This could be a very bad thing for bats for several reasons. To understand how bad this infection could be to the future of WNS in North America, researchers will need to determine its source and any sexual compatibility with existing isolates. </p>
<h2>Tougher than your average spore</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/119722/original/image-20160421-26988-8o6v7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119722/original/image-20160421-26988-8o6v7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=388&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119722/original/image-20160421-26988-8o6v7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=388&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119722/original/image-20160421-26988-8o6v7v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=388&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119722/original/image-20160421-26988-8o6v7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=487&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119722/original/image-20160421-26988-8o6v7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=487&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119722/original/image-20160421-26988-8o6v7v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=487&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Electron micrograph of <em>P. destructans</em>. Asexual spores (conidia) are rendered blue.</span>
<span class="attribution"><span class="source">John Neville, Georgia State University</span></span>
</figcaption>
</figure>
<p>The spores (reproductive cells produced by fungi) that are produced in asexual reproduction are known as conidia. All the current work being conducted to make spores inactive to control the spread of WNS are predicated on the sensitivity of these conidia to a given control agent. </p>
<p>Yet the phylum of this fungus, known as Ascomycota, can reproduce in another way – sexually, through a type of spore known as ascospores. In numerous examples in other Ascomycota, it has been shown that ascospores are more resistant to control methods than conidia.</p>
<p>If researchers find that the particular <em>P. destructans</em> fungus is capable of producing ascospores – that is reproducing sexually, rather than asexually as with conidia – then current decontamination protocols will need to be revised to address the increased resilience of these sexual spores.</p>
<h2>A Red Queen and brown bats</h2>
<p>The ultimate significance of whether the fungus reproduces sexually involves a long-debated theory of evolutionary biology that <a href="http://www.academia.edu/9320131/Reign_of_the_Red_Queen_The_future_of_bats_hangs_in_the_balance">many have been hopeful will ultimately save susceptible North American bat species</a>: the Red Queen hypothesis. </p>
<p>The idea is that in a system with a host (bat) and parasite (<em>P. destructans</em>), coevolution occurs as the disease recurs through numerous generations. If only the host is reproducing sexually (i.e., WNS in North America) and generating greater variation with each generation, the host will be able to evolve a tolerance to the parasite.</p>
<p>However, in a system where both the host and parasite reproduce sexually, coevolution supports the status quo. So as bats evolve tolerance to one strain of <em>P. destructans</em> another strain resulting from sexual recombination that is capable of causing disease in the new tolerant host will become the dominant strain. </p>
<p>Thus, the analogy of the Red Queen running in place in “Through the Looking-Glass, and What Alice Found There” by Lewis Carroll. Although evolution is occurring (running), everyone is evolving together so the disease paradigm never changes. </p>
<p>This is the possibility the introduction of a complementary mating type presents to WNS in North America. Bats won’t be able to evolve a significant tolerance as the fungus reproduces sexually and rapidly adapts to any resistance the bats develop. </p>
<h2>Bats everywhere but not a hibernacula to treat</h2>
<p>In addition to the strategic and biological challenges that a Pacific Coast WNS case may introduce, there is also a major logistical challenge that has been looming over the WNS community: where are hibernacula – the shelters where bats hibernate – in the west? </p>
<p>Currently there are no known little brown bat hibernacula in Washington. This doesn’t mean that bat ecologists think little brown bats don’t hibernate in Washington, but rather they have <a href="http://wdfw.wa.gov/publications/01504/wdfw01504.pdf">never been able to find large hibernacula</a> as is common in the eastern U.S. </p>
<p>Treating bats during the spring, summer and fall when they are widely dispersed on the landscape is impractical. The effort it takes to capture a few individuals is not scalable to an extent that could have a significant impact on WNS-related population declines. That is why most efforts to develop management strategies have been focused on intervention during the winter at known hibernacula where large groups of bats could be treated together with reasonable effort. </p>
<p>If any of the treatments currently under investigation were available today, how could they be used in Washington? Without understanding how these western bat species use the landscape and where they hibernate, there is no way to deliver any future management tool. </p>
<h2>Bad, badder, baddest</h2>
<p>In many ways this new western case changes the paradigm of WNS. </p>
<p>In the worst-case scenario, a complementary strain has been introduced into North America and will eventually find its way to locations where the East Coast strain exists, facilitating a more recalcitrant and adaptable pathogen. </p>
<p>In the best-case scenario, this case represents a loss of containment within North America, reducing the value of efforts to slow the westward spread of WNS while treatments can be developed and western bat hibernacula can be identified. Either way, the news of a WNS-positive bat in Washington state represents another disaster for bats that are already experiencing unprecedented declines.</p><img src="https://counter.theconversation.com/content/57320/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Cornelison receives funding from the USDA Forest Service, US Fish and Wildlife Service, Bat Conservation International, The Nature Conservancy, FightWNS, Basically Bats, and The Conservation Fund for his white-nose syndrome related research.</span></em></p>More bad news for America’s beleaguered bats as white nose syndrome spreads to the West Coast. A wildlife biologist explains why this change has the bat community so worried.Christopher T. Cornelison, Postdoctoral Research Associate, Georgia State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/521912016-01-19T08:46:55Z2016-01-19T08:46:55ZNew genetically engineered American chestnut will help restore the decimated, iconic tree<figure><img src="https://images.theconversation.com/files/108328/original/image-20160115-7357-62ahtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Transgenic American chestnuts could soon take root.</span> <span class="attribution"><span class="source">Claire Dunn</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>American chestnut trees were once among the most majestic hardwood trees in the eastern deciduous forests, many reaching 80 to 120 feet in height and eight feet or more in diameter.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=873&fit=crop&dpr=1 600w, https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=873&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=873&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1097&fit=crop&dpr=1 754w, https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1097&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/107550/original/image-20160107-13988-1hmnccu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1097&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Historic picture of a large American chestnut tree (Ten Eyck Dewitt barns, Paul Farm, NY).</span>
<span class="attribution"><span class="source">Provided by Gail Whistance</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>The “then boundless chestnut woods” Thoreau wrote about in Walden once grew throughout the Appalachian mountains. They provided habitat and a mast crop for wildlife, a nutritious nut crop for humans and a source of valuable timber. Because of their rapid growth rate and rot-resistant wood, they also have significant <a href="http://dx.doi.org/10.1016/j.foreco.2009.04.014">potential for carbon sequestration</a>, important in these days of climate change.</p>
<p>The species has a sad story to tell. Of the estimated four billion American chestnut trees that once grew from Maine to Georgia, <a href="http://dx.doi.org/10.3390/f7010004">only a remnant survive today</a>. </p>
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<a href="https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=488&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=488&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=488&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=613&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=613&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108326/original/image-20160115-7383-3kuywn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=613&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A ghost forest of blighted American chestnuts in Virginia.</span>
<span class="attribution"><a class="source" href="http://www.loc.gov/pictures/item/va1798.photos.192521p/">Library of Congress Prints and Photographs Division</a></span>
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<p>The species was nearly wiped out by chestnut blight, a devastating disease caused by the exotic fungal pathogen <em>Cryphonectria parasitica</em>. This <a href="http://dx.doi.org/10.1094/APSnetFeature-2000-1200">fungus was accidentally introduced</a> into the United States over a century ago as people began to import Asian species of chestnut. It reduced the American chestnut from the dominant canopy species in the eastern forests to little more than a rare shrub.</p>
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<a href="https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=805&fit=crop&dpr=1 600w, https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=805&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=805&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1012&fit=crop&dpr=1 754w, https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1012&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/107551/original/image-20160107-13986-1emirfg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1012&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Chestnut blight canker.</span>
<span class="attribution"><span class="source">William Powell</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>After battling the blight for more than a century, researchers are using the modern tools of breeding, <a href="http://www.ct.gov/caes/cwp/view.asp?a=2815&q=376826">bio-control</a> methods that rely on a virus that inhibits the growth of the infecting fungus, and direct genetic modification to return the American chestnut to its keystone position in our forests. </p>
<p>To restore this beloved tree, we will need every tool available. It’s taken 26 years of research involving a team of more than 100 university scientists and students here at the not-for-profit <a href="http://www.esf.edu/chestnut/">American Chestnut Research and Restoration Project</a>, but we’ve finally developed a nonpatented, blight-resistant American chestnut tree.</p>
<h2>One genetic tweak</h2>
<p>My research partner, Dr. Chuck Maynard, and I work with a team at the SUNY College of Environmental Science and Forestry (<a href="http://www.esf.edu/welcome/">ESF</a>) that includes high school students, undergraduate and graduate students, postdoctoral fellows, colleagues from other institutions and volunteers. Our efforts focus on direct genetic modification, or genetic engineering, as a way to bring back the American chestnut.</p>
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<figcaption>
<span class="caption">Thirty days after infection with chestnut blight, the wild-type American chestnuts on the left are wilted, while the ‘Darling 54’ transgenic trees are doing well.</span>
<span class="attribution"><span class="source">Andy Newhouse</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>We’ve tested more than 30 genes from different plant species that could potentially enhance blight resistance. To date, a gene from bread wheat has proven <a href="http://dx.doi.org/10.1007/s11248-013-9708-5">most effective</a> at <a href="http://dx.doi.org/10.1016/j.plantsci.2014.04.004">protecting the tree</a> from the fungus-caused blight.</p>
<p>This wheat gene produces an enzyme called oxalate oxidase (OxO), which detoxifies the oxalate that the fungus uses to form deadly cankers on the stems. This common defense enzyme is found in all grain crops as well as in bananas, strawberries, peanuts and other familiar foods consumed daily by billions of humans and animals, and it’s unrelated to gluten proteins. </p>
<p>We’ve added the OxO gene (and a marker gene to help us ensure the resistance-enhancing gene is present) to the chestnut genome, which contains around 40,000 other genes. This is a minuscule alteration compared to the products of many traditional breeding methods. Consider the techniques of species hybridization, in which tens of thousands of genes are added, and mutational breeding, in which unknown mutations are induced. Genetic engineering allows us to produce a blight-resistant American chestnut that’s genetically over 99.999 percent identical to wild-type American chestnuts.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/Ty9b1vml5IQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Time release video of seedling exposed to chestnut blight.</span></figcaption>
</figure>
<h2>Gene transfers happen all the time</h2>
<p>For some, this raises a question: isn’t moving genes between species unnatural? In short: no. Such movement has been essential to the evolution of all species. Researchers are discovering that horizontal (between-species) gene transfer happens in nature and <a href="http://www.sciencemag.org/news/2015/03/humans-may-harbor-more-100-genes-other-organisms">even in our own bodies</a>. In fact, the same organism (<em>Agrobacterium</em>) that <a href="http://dx.doi.org/10.1128/MMBR.67.1.16-37.2003">we use to move blight-resistance genes</a> into chestnuts has also permanently modified other plants in the wild. For example, all the sweet potato varieties on the market today were <a href="http://dx.doi.org/10.1073/pnas.1419685112">genetically engineered by this bacterium around 8,000 years ago</a>.</p>
<p>There is another logical question: what about unintended consequences? Of course undefined questions are impossible to answer, but logically the method producing the smallest changes to the plant should have the fewest unintended consequences. We have not observed nontarget transgene effects – that is, changes that we didn’t intend – on our trees or on other organisms that interact with our trees, for example <a href="http://dx.doi.org/10.1128/AEM.02169-14">with beneficial fungi</a>.</p>
<p>And at any rate, unintended consequences aren’t constrained to the genetics lab. Chestnut growers have seen unintended consequences resulting from their hybrid breeding of chestnuts. One example is the internal kernel breakdown (<a href="http://msue.anr.msu.edu/topic/chestnuts/horticultural_care/internal_kernal_breakdown">IKB</a>) seen in <a href="http://dx.doi.org/10.17660/ActaHortic.2014.1019.14">chestnut hybridization</a>, caused by crossing a male sterile European/Japanese hybrid (“Colossal”) with Chinese chestnut. By mixing tens of thousands of genes with unknown interactions through traditional breeding, occasionally you get incompatible combinations or induced mutations that can lead to unintended outcomes like IKB or male sterility.</p>
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<figcaption>
<span class="caption">Butterfly on male flowers of an American chestnut.</span>
<span class="attribution"><span class="source">Andy Newhouse</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
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<p>One of the key advantages of genetic engineering is that it’s far less disruptive to the original chestnut genome – and thus to its ecologically important characteristics. The trees remain more true to form with less chance of unforeseen and unwanted side effects. Once these genes are inserted, they become a normal part of the tree’s genome and are inherited just like any other gene. They have no more chance of moving to other species than do any of the approximately 40,000 genes already in chestnut.</p>
<h2>Next steps for the blight-resistant American chestnut</h2>
<p>One of the challenges of genetic engineering that is not faced by any other methods of genetic modification also serves as a safeguard. We must shepherd these trees through federal regulatory review by the U.S. Department of Agriculture, the Environmental Protection Agency and the Food and Drug Administration. Our plan is to submit these applications as we finish collecting the necessary data; we expect the process to take three to five years. Once we receive (anticipated) approval, we will quickly make the trees available to the public.</p>
<p>This project is unique because it is the first to seek approval of a transgenic plant to help save a species and restore a forest’s ecology. Our forests face many challenges today from exotic pests and pathogens such as Emerald Ash Borer, Hemlock Wooly Adelgid, Sudden Oak Death, Dutch Elm Disease, and many more. The American chestnut can serve as a model system for protecting our forest’s health.</p>
<p>Direct genetic modification will likely not be used in isolation. Integration might improve the outcomes of both the conventional hybrid/backcross breeding program of the <a href="http://www.acf.org">American Chestnut Foundation</a> and our genetic engineering program. Allowing crosses between the best trees from both programs will allow gene stacking – having multiple and diverse resistance genes in a single tree – with each working in a different way to stop the blight. This would significantly decrease the chances that the blight could ever overcome the resistance. The two programs working together would also allow the addition of resistance genes for other important pests, such as <em>Phytophthora</em>, which causes a serious root rot in the southern part of the chestnut range. And combining methods increases the chances that the resistance will be long-lasting and reliable, which is very important for a tree that in good health can live for centuries.</p>
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<figcaption>
<span class="caption">Transgenic American chestnut ‘Darling 54.’</span>
<span class="attribution"><span class="source">Linda McGuigan</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
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<p>A unique aspect of the genetically engineered American chestnut trees is their ability to rescue the genetic diversity in the small surviving population of American chestnut trees. When we cross our blight-resistant transgenic trees to these surviving <a href="https://nysufctakingroot.wordpress.com/2016/01/15/participate-in-the-reintroduction-of-the-american-chestnut-by-simply-planting-a-few-nuts/">“mother” trees</a>, directly in the wild or from nuts gathered from them and grown in orchards, we’re helping preserve the remaining wild genes.</p>
<p>Half the resulting offspring will be fully blight-resistant, while also containing half the genes from the mother tree. By making these crosses, the restoration trees will be ecologically adapted to the diverse environments in which they’ll grow. These trees could also be used to boost the genetic diversity of the hybrid/backcross breeding program, or used directly for restoration and left to fend for themselves, allowing natural selection to make the final determination of the effectiveness of our efforts.</p>
<p>The American chestnut was one of the most important hardwood tree species in the eastern forests of North America, and it can be again. This tiny change in the genome will hopefully be a huge step toward putting the American chestnut on a path to recovery.</p><img src="https://counter.theconversation.com/content/52191/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Powell is a non-paid consultant to The American Chestnut Foundation. Current external funding includes The American Chestnut Foundation (National and NY Chapter), USDA NIFA Biotechnology Risk Assessment Grant (BRAG), 10,000 Chestnut Challenge Crowd Funding Campaign, New York State Legislature Grant, Mississippi Fish and Wildlife Foundation, Camp Fire Club of America and public donations. Additional past funders are listed on our chestnut website pages: <a href="http://www.esf.edu/chestnut/">http://www.esf.edu/chestnut/</a> Dr. Powell is also a member of The American Chestnut Foundation, the Arbor Day Foundation, the American Phytopathological Society, the American Society for Microbiology, and the International Society for Horticultural Science.</span></em></p>Adding a single wheat gene helps the American chestnut withstand a fungal pathogen that nearly wiped these hardwood trees out of the eastern forests they once dominated.William Powell, Professor in the Department of Environmental and Forest Biology, State University of New York College of Environmental Science and ForestryLicensed as Creative Commons – attribution, no derivatives.