Editing Chestnut blight

{{Short description|Fungus disease of chestnut trees}}
{{Speciesbox
| name = Chestnut blight fungus
| image = Chestnut blight.jpg
| image_caption = Cankers caused by the fungal infection cause the bark to split.
| taxon = Cryphonectria parasitica
| authority = ([[William Alphonso Murrill|Murrill]]) [[M.E.Barr]] (1978)
| synonyms = *''Diaporthe parasitica'' <small>Murrill (1906)</small>
}}

The [[pathogen]]ic fungus '''''Cryphonectria parasitica''''' (formerly ''Endothia parasitica'') is a member of the [[Ascomycota]] (sac fungi). This [[necrotrophic]] fungus is native to East Asia and South East Asia and was introduced into Europe and North America in the early 1900s.<ref name=Mlinarec-2018 /> Strains of the fungus spread more or less rapidly and caused significant tree loss in both regions.  Strains of the fungus can be more or less virulent.

==Overview==
''Cryphonectria parasitica'' is a parasitic [[fungus]] of [[chestnut]] trees. This disease came to be known as '''chestnut blight'''. Naturally found in South East Asia, accidental introductions led to invasive populations of ''C. parasitica'' in North America and Europe. In the first half of the 20th century, the fungal disease had a devastating economic and social impact on communities in the eastern United States.  It killed an estimated four billion trees;<ref name="Roane-et-al-1986"/> or, by another count, 3.5 billion trees through 2013.<ref name="Fisher-et-all 2012"/> Less severe impacts have occurred in Europe due to widespread [[Hypovirus|CHV1]]-induced ''[[hypovirulence]]''.<ref name="ACF-biocontrol" /> CHV1 is one of at least two [[Mycovirus|viral pathogens that weaken the fungus]] through hypovirulence and helps trees survive a blight infection.<ref name=Milgroom/><ref name=Hypovirulence/>

The [[American chestnut]] (''Castanea dentata'') and [[Castanea pumila|American chinquapin]] (''Castanea pumila'') are highly susceptible to chestnut blight. The [[Castanea sativa|European chestnut]] (''Castanea sativa'') is also susceptible, but due to widespread CHV1 hypovirulence, blight-induced tree death is less common.<ref name=Robin/> The fungus can infect other tree species such as [[oak]]s, [[red maple]]s, [[staghorn sumac]]s, and [[shagbark hickory|shagbark hickories]].<ref name=Missouri-Botanical-Garden/> Once infected, these trees' bark also exhibit orange cankers but may not die. The pathogen can persist in these trees, producing [[spore]]s that may infect other trees.

Fungal strains spread by wind-borne [[ascospores]] and, over a shorter distance, [[conidia]] distributed by rain-splash action.<ref name=Forest-Pathology/> Infection can be local in range, so some isolated American chestnuts survive where there is no other infected tree within {{cvt|10|km}}. Soil organisms at the root collar and root system of the chestnut tree are antagonistic to the fungus. Chestnut tree roots are resistant to blight infections.  Consequently, a large number of small American chestnut trees still exist as [[Shoot (botany)|shoot]]s growing from existing root bases. However, these regrown shoots seldom reach the sexually reproductive stage before above ground growth is again girdled by the fungus.<ref name=Appalachian-Woods/>
Fungal strains originally infected the [[Castanea mollissima|Chinese chestnut]] (''Ca. mollissima'') and the Japanese chestnut (''Ca. crenata''). These two species have co-evolved with the pathogen, making them most variably resistant to its ill effects.<ref name=Rigling/>

==History==
[[File:Castanea dentata - blight 1.jpg|thumb|right|250px|Chestnut blight affecting a young American chestnut]]

===Infections in North America===

In 1904, the chestnut [[blight]] was accidentally introduced to North America.  ''Cryphonectria parasitica'' was introduced into the United States from [[East Asia]] via import of [[Castanea crenata|Japanese chestnut trees]]. Commercial breeding purposes motivated these imports.<ref name=Columbia/><ref name=Miller/> Infection of American chestnut trees with ''C. parasitica'' simultaneously appeared in numerous places on the East Coast, most likely from Japanese chestnuts, which had become popular imports.<ref name="American-chestnut"/>

Herman W. Merkel, a forester at the [[Bronx Zoo|New York Zoological Garden]] (Bronx Zoo) first found infected chestnut trees on the grounds of the zoo. 
In 1905, American mycologist [[William Murrill]] isolated and described the fungus responsible (which he named ''Diaporthe parasitica''), and [[Koch's postulates|demonstrated by inoculation into healthy plants]] that the fungus caused the disease.<ref>{{cite journal | vauthors = Rogerson CT, Samuels GJ | year = 1996 | title = Mycology at the New York Botanical Garden, 1985-1995 | url = https://zenodo.org/record/1232568| journal = Brittonia | volume = 48 | issue = 3| pages = 389–98 | doi=10.1007/bf02805308| s2cid = 32145426 }}</ref> By 1940, most mature American chestnut trees had been girdled by the disease.<ref name="American-chestnut"/> It took about 40 years to devastate the nearly four-billion-strong American chestnut population in North America.<ref>{{Cite web |url=http://www.acf.org/history.php |title=The American Chestnut Foundation - Mission & History |access-date=2009-03-08 |archive-date=2008-05-16 |archive-url=https://web.archive.org/web/20080516030808/http://acf.org/history.php |url-status=dead }}</ref> Only a few clumps of uninfected trees remained in [[Michigan]], [[Wisconsin]], and the [[Pacific Northwest]].

Japanese and Chinese chestnut trees<ref name="Blight-resistance" /> may resist an infection from ''C. parasitica''.<ref>{{Cite web |url=http://acf.org/history.php |title=History of The American Chestnut Foundation |access-date=2019-06-29 |archive-date=2008-05-16 |archive-url=https://web.archive.org/web/20080516030808/http://acf.org/history.php |url-status=dead }}</ref> Because of the disease, American chestnut wood almost disappeared from the market for decades, although it can still be obtained as [[reclaimed lumber]].<ref name=Edlin/>

It is estimated that in some places, such as the [[Appalachian Mountains]], one in every four [[hardwood]]s was an American chestnut. Mature trees often grew straight and branch-free for 50 feet and could grow up to 100 feet tall with a trunk diameter of 14 feet at a few feet above ground level. The reddish-brown wood was lightweight, soft, easy to split, very resistant to decay, and did not warp or shrink. For three centuries many [[barn]]s and homes near the [[Appalachian Mountains]] were made from American chestnut.<ref name=Salem /> Its straight-grained wood was ideal for building furniture and caskets. The bark and wood were rich in tannic acid, which provided tannins for use in the tanning of leather.<ref>[http://ecosystems.psu.edu/research/chestnut/information/conference-2004/conference/davis Davis Conference 2004], ecosystems.psu.edu</ref>

Chestnuts were an important cash crop and food source.  Many native animals fed on chestnuts, and chestnuts were used for livestock feed, which kept the cost of raising livestock low.<ref>American-Chestnut: Appalachian Apocalypse, Cornett Media, 2010.</ref>

Efforts started in the 1930s and are still ongoing, in [[Massachusetts]]<ref name="Thys"/> and many other places<ref name="dof.virginia.gov" /> in the United States, to repopulate chestnut trees.<ref name="acf">[http://www.tacf.org/ American Chestnut Foundation].</ref>  Surviving American chestnut trees are being bred for resistance to the blight, notably by [[The American Chestnut Foundation]], which aims to reintroduce a blight-resistant American chestnut to its original forest range within the early decades of the 21st century.<ref>{{cite web |url=http://www.fs.fed.us/r8/chestnut/qa.php |title=American Chestnut Restoration Project - USDA Forest Service - Southern Region |access-date=2013-09-11 |archive-url=https://web.archive.org/web/20121223044518/http://www.fs.fed.us/r8/chestnut/qa.php |archive-date=2012-12-23 }}</ref> [[Japanese Chestnut|Japanese chestnut]] and [[Castanea mollissima|Chinese chestnut]], as well as Seguin's chestnut and Henry's chestnut, have been used in these breeding programs in the US to create disease-resistant [[Hybrid (biology)|hybrid]]s with the American chestnut.<ref name="rhs">''New RHS Dictionary of Gardening''. By A. Huxley ed. 1992. Macmillan {{ISBN|0-333-47494-5}}.</ref>  Chinese chestnut trees have been found to have the highest resistance to chestnut blight;<ref name="Blight-resistance" /> however, individuals within the Chinese chestnut species may vary in blight resistance. Some individuals are still quite susceptible while others are essentially immune.<ref>Dr. Greg Miller, Empire Chestnut Company, FAQ http://www.empirechestnut.com/faqpests.htm {{Webarchive|url=https://web.archive.org/web/20160113045455/http://www.empirechestnut.com/faqpests.htm |date=2016-01-13 }} Retrieved January 13, 2016</ref>

Hypovirulence is not widespread in the US and attempts to commercially introduce CHV1 virus have not been widely successful {{citation needed|date=September 2024}}. Though CHV1 persists in applied trees, it does not spread naturally as it does in Europe {{why?|date=September 2024}}, preventing it from being an effective form of [[Biological pest control|biocontrol]].

===Infections in Europe===

In 1938, chestnut blight was first identified around [[Genoa]]. Infection quickly spread and was identified in France in 1946, Switzerland in 1951, and Greece in 1963. It has most recently been found in the UK. Due to genetic differences between the fungal populations (strains), it is likely that a second introduction of chestnut blight occurred in [[Georgia (country)|Georgia]] and [[Azerbaijan]] in 1938.<ref>{{Cite journal|last=Prospero |first=S |title=Discovery of a new gene pool and a high genetic diversity of the chestnut blight fungus ''Cryphonectria parasitica'' in Caucasian Georgia |journal=Infection, Genetics and Evolution|volume=20|date=December 2013 |pages=131–139|doi=10.1016/j.meegid.2013.08.009 |pmid=23994123 }}</ref><ref>{{Cite journal|last=Rigling|first=Daniel|date=December 2018|title=Genetic and Phenotypic Characterization of ''Cryphonectria hypovirus 1'' from Eurasian Georgia|url= |journal=Viruses|volume=10 |number=12|page=687|doi=10.3390/v10120687|pmid=30513977|pmc=6315935|doi-access=free}}</ref> The fungal infections initially caused widespread tree death in Europe. However, in the early 1950s trees were identified in Italy that survived fungal infection. On these trees, the fungus caused more superficial cankers, that appeared to be healing. The milder infection outcome was due to the presence of CHV1, an [[RNA virus]] that infects ''C. parasitica''. CHV1 spread naturally throughout Europe but is also spread artificially as a biocontrol measure (particularly in France). CHV1 is currently not present in the UK, Northern France, or Eastern Georgia but an introduction for biocontrol is being considered. {{Citation needed|date=January 2024}}

==Symptoms==
[[File:Chestnut blight on cut tree in Adams County Ohio.jpg|thumb|left|A chestnut tree that has been felled, with blight on its inner bark and trunk]]
The fungus enters through wounds on susceptible trees and grows in and beneath the bark, eventually killing the [[Cork cambium|cambium]] all the way around the twig, branch, or trunk.<ref>Anagnostakis SL (2000) Revitalization of the Majestic Chestnut: Chestnut Blight Disease.</ref> The first symptom of ''C. parasitica'' infection is a small orange-brown area on the tree bark. A sunken [[canker]] then forms as the [[mycelium|mycelial]] fan spreads under the bark. As the [[hypha]]e spread, they produce several toxic compounds, the most notable of which is [[oxalic acid]]. This acid lowers the pH of the infected tissue from around the normal 5.5 to approximately 2.8, which is toxic to cambium cells. The canker eventually girdles the tree, killing everything above it. Distinctive yellow [[tendril]]s (cirrus) of [[Conidium|conidia]] can be seen extruding in wet weather.<ref>Crop Protection Compendium 2005 Edition. ''Cryphonectria parasitica'' (blight of chestnut). CAB International, Wallingford, UK.</ref>

==Life cycle and reproduction==
The primary plant tissues targeted by ''C. parasitica'' are the inner bark, an area containing the conductive tissue, and the cambium, a layer of actively dividing cells that give rise to secondary vascular tissues. In these tissues, the pathogen forms diffuse cankers in which the mycelium overwinters.<ref name="Chestnut blight"/> In the following spring, two types of fruiting bodies will form: [[pycnidia]], usually first, and [[perithecia]].<ref name="Chestnut blight"/> Following rainfall, the pycnidia ooze orange tendrils of conidia, the asexual spores, while perithecia forcibly eject ascospores, the sexual spores.<ref name="Chestnut blight"/><ref name=":1">{{Cite web|url=http://www.forestpathology.org/dis_chestnut.html|title=Forest Pathology - Chestnut Blight|website=www.forestpathology.org|access-date=2017-12-15}}</ref> Upon becoming airborne, ascospores are carried by eddies of wind to new hosts or infect other parts of the same tree.<ref name="Chestnut blight"/> When insects, birds, or other wildlife come into contact with the cankers, they can mechanically disperse the conidia to a new host.<ref name="Chestnut blight"/><ref name=":1" /> Additionally, the asexual spores can be dispersed by rain splash.<ref name=":1" /> Once on the new host, or new area of the tree, the spores can germinate and infect the inner bark through insect wounds and fissures in the outer bark.

If cankers continue to form and expand, the fungus can girdle the stem, severing the flow of nutrients and water to the vital vegetative tissues. The absence of nutrient dispersal will result in above ground tree death.  However, the root system may survive. As a result, American chestnuts exist mainly as shrubs sprouting from the old, surviving roots.<ref name=":1" /> These sprouts usually die of infection by ''C. parasitica'' before reaching sexual maturity.

{{anchor|Management|Hypovirulence|Hypovirus|Sanitation|Chemical control}}

==Management: hypovirulence, sanitation, and chemical control==
In Europe, during the late 1960s, it was found that a strain of ''C. parasitica'' was less virulent, only able to produce shallow cankers that the tree's callus tissue could eventually limit and isolate. The trait of hypovirulence could be transferred from an avirulent strain to a lethal strain through [[anastomosis]]—the fusion of hyphae.<ref name=":2">{{Cite journal|last=Nuss|first=Donald|date=1992|title=Biological control of chestnut blight: an example of virus-mediated attenuation of fungal pathogenesis|journal=Microbiological Reviews|volume=56 | issue = 4 |pages=561–576|doi=10.1128/MMBR.56.4.561-576.1992|pmid=1480109|pmc=372888}}</ref> It was later discovered that this attenuated virulence was due to infection by a [[dsRNA]] [[mycovirus]], ''Cryphonectria hypovirus 1'' (CHV1) of genus ''[[Hypovirus]]''.<ref name=":3">{{Cite journal|vauthors=Kazmierczak P, McCabe P, Turina M, Wilk DJ, Van Alfen NK|date=June 2012|title=The Mycovirus CHV1 Disrupts Secretion of a Developmentally Regulated Protein in ''Cryphonectria parasitica''|journal=Journal of Virology|volume=86 | issue = 11 |pages=6067–6074|doi=10.1128/jvi.05756-11|pmid=22438560|pmc=3372201}}</ref><ref name="ACF-biocontrol" />

Considering the nature of hypovirulent strains, there has been a strong interest to use them to manage lethal ''C. parasitica'' strains. In Europe, natural dissemination of hypovirulence in pathogen populations resulted in the restoration of economically valuable chestnuts.<ref name=":2" /> Unfortunately, this was not the case in the United States. Compared to Europe, the US has a greater diversity of ''C. parasitica'' strains.<ref>{{Cite journal|last=Thompson|first=Helen|date=October 2012|title=Plant science: the chestnut resurrection|journal=Nature|volume=490|issue=7418|pages=22–23|doi=10.1038/490022a|pmid=23038446|bibcode=2012Natur.490...22T|doi-access=free}}</ref> Thus, the spread of the mycovirus in American ''C. parasitica'' populations is inhibited by vegetative incompatibility, an [[allorecognition]] system that inhibits the fusion of hyphae between individuals that are genetically distinct at specific loci.<ref name=":3" /><ref name=":2" /> In 2016, however, "super mycovirus donor strains" of ''C. parasitica'' were engineered to overcome this incompatibility system.  This could potentially be employed as a method of biological control.<ref>{{Cite journal|vauthors=Zhang DX, Nuss DL|date=2016|title=Engineering super mycovirus donor strains of chestnut blight fungus by systematic disruption of multilocus vic genes|journal=PNAS|volume=113 | issue = 8 |pages=2062–2067|doi=10.1073/pnas.1522219113|pmid=26858412|pmc=4776480|bibcode=2016PNAS..113.2062Z|doi-access=free}}</ref>

As mentioned above some soil microorganisms suppress ''C. parasitica''. This can be used to treat the cankers, by using a soil compress, a quantity of soil held against the trunk itself with [[plastic wrap]] and some [[adhesive tape]] around that.<ref name="ACF-biocontrol" />

In addition to biocontrol, chestnut blight can also be managed by sanitation practices and chemical control; however, such management strategies are only feasible on a small scale, such as in an orchard. Sanitation practices like the pruning of symptomatic limbs and removal of infected trees can serve to eliminate sources of inoculum and limit the spread of the pathogen.<ref name="Chestnut blight"/>

Additionally, some fungicides may be effective at controlling this fungal disease. A study on the chemical control of chestnut blight in ''Castanea sativa'', may have found that the external application of both [[copper oxychloride]] and [[carbendazim]] could reduce the rate of disease by almost 50%.<ref>{{Cite journal|vauthors= Trapiello, Estefanía, et al.|title=Chestnut Blight Control by Agrochemicals in Castanea Sativa under Managed Conditions|journal= Journal of Plant Diseases and Protection |volume= 122 |issue=3 |publisher=Verlag Eugen Ulmer KG |year=2015 |pages=120–24 |doi=10.1007/BF03356540|jstor=24618945|s2cid=87736296 }}</ref>

==Conservation efforts in North America==
[[File:Tower Hill Botanic Garden - American chestnuts.jpg|thumb|right|250px|Experimental trials by [[The American Chestnut Foundation]] at [[Tower Hill Botanic Garden]] in [[Massachusetts]]]]
[[File:castanea dentata-field trial2009.jpg|thumb|upright|American chestnut field trial sapling from the American Chestnut Cooperators Foundation]]
There are approximately 2,500 chestnut trees growing on {{convert|60|acre|ha}} near [[West Salem, Wisconsin]], which is the world's largest remaining stand of American chestnut. These trees are the descendants of those planted by Martin Hicks, an early settler in the area. In the late 1800s, Hicks planted fewer than a dozen chestnuts. Planted outside the natural range of American chestnut, these trees escaped the initial wave of infection by chestnut blight, but in 1987 scientists found blight also in this stand. There is a program to bring American chestnut back to the Eastern forest funded by the [[American Chestnut Foundation]], [[Wisconsin Department of Natural Resources]], [[USDA Forest Service]], [[West Virginia University]], [[Michigan State University]], and [[Cornell University]].<ref name="Chestnut's-Last-Stand" />

Removing blighted trees to control the disease was first attempted when the blight was discovered, but this proved to be an ineffective solution. Scientists then set out to introduce a [[hyperparasite|hyperparasitic]] [[hypovirus]] into the chestnut blight fungus. The trees infected with virus-treated fungus responded immediately and began to heal over their cankers. However, the virus was so efficient at attenuating fungal growth that it prevented the spreading of the virus from an infected fungus growing on one tree to that growing on another tree. Only the virus-treated trees recovered. Scientific opinion regarding the future of the stand varies.<ref name="Chestnut's-Last-Stand"/>

===Hybrid chestnut trees===
Current efforts are underway by the Forest Health Initiative to use modern breeding techniques and genetic engineering to create resistant tree strains, with contributions from [[SUNY College of Environmental Science and Forestry]], [[Pennsylvania State University]], the [[University of Georgia]], and the [[United States Forest Service]]. One of the most successful methods of breeding is to create a [[Backcrossing|back cross]] of a resistant species (such as one from China or Japan) and American chestnut. Researchers identified two or three genes that allow for blight resistance, and are focusing on giving the American chestnut hybrids only those genes from the Chinese or Japanese chestnut.<ref>{{Cite web|url=http://www.acf.org/pdfs/about/restoration.pdf|archive-url=https://web.archive.org/web/20071108102851/http://www.acf.org/pdfs/about/restoration.pdf|archive-date=2007-11-08|title=Restoring the American Chestnut|website=The American Chestnut Foundation}}</ref>

The two species are first bred to create a 50/50 hybrid. After three backcrosses with American chestnut, the remaining genome is approximately 1/16 that of the resistant tree and 15/16 American. The strategy is to [[Selection (biology)|select]] blight-resistance genes during the backcrossing while preserving the more wild-type traits of American chestnut as the dominant [[phenotype]]. Thus, the newly bred hybrid chestnut trees should reach the same heights as the original American chestnut. Many of these 15/16 American chestnut hybrids have been planted along the East Coast, including in the Jefferson National Forest and on the [[Flight 93 National Memorial]]. Some of these sites have had researchers check on the saplings that have been planted to see their survival rate. For the hybrids to do well, they need areas with decent drainage and abundant sunlight.<ref>{{Cite web |title=The American Chestnut Foundation - Mission & History |url=https://tacf.org/about-us/ |archive-url=https://web.archive.org/web/20080516030808/http://acf.org/history.php |archive-date=2008-05-16 |access-date=2016-11-13 |website=www.tacf.org}}</ref> Meeting these needs can be hard to do, so not all restoration areas have been successful with hybrid survival.

===Transgenic blight-resistant chestnut trees===
A 1983 study on [[hypovirulence]] had shown that chestnut blight infected with hypovirus produced less oxalic acid when attacking the [[cambium]].<ref name="Havir-Anagnostakis-1983" /><ref name="Chen-et-al-2010" /> Meanwhile, a [[plant pathologist]], Dr. William Powell, had been trying to figure out how to transfer all of the Asian chestnut's resistance genetics to its American relatives. In the 1990s, he had the idea to give up on the more complicated and larger job, and instead look around for a single gene elsewhere.<ref name="Sierra-Club-transgenic" /> (In related work, in 2001 Liang, Mayard, Allen, and Powell successfully inserted an [[oxalate oxidase]] (OxO) gene from [[wheat]] into ''[[Populus × canadensis|Populus × euramericana]]'' ("Ogy") for ''[[Septoria musiva]]'' resistance.<ref name="Liang-et-al-2001" /> This enzyme breaks down the [[oxalic acid]] secreted by the fungus into carbon dioxide and hydrogen peroxide.) In 2007, Welch, Stipanovic, Maynard, and Powell showed that transgenic ''C. dentata'' expressing a wheat OxO indeed had lower [[lignin]] degradation by oxalic acid, and suggested this was the path to take.<ref name="Welch-et-al-2007" /><ref name="Chen-et-al-2010" />

A few years later this line of research culminated in the final product: Powell<ref name="Templeton-Powell" /><ref name="Plantopia" /><ref name="Plantopia-Powell" /> and another plant pathologist, Dr. Charles Maynard, working at the [[State University of New York College of Environmental Science and Forestry]] developed [[American chestnut]]s which had heightened [[blight resistance]]. Heightened resistance was attained by introducing a wheat OxO gene into the American chestnut genome. (Because an unrelated gene was transferred, this did not make the chestnut trees produce [[gluten]], and the nuts remain [[gluten-free diet|gluten free]].)<ref name="Cornell-Powell-gluten" /> The [[transgenic]] trees have blight resistance either equal to or surpassing that of ''[[Castanea mollissima]]'', Chinese chestnuts.<ref name="Zhang-et-al-2013" /> 
In 2013, SUNY ESF had over 100 individual events being tested, with more than 400 slated to be in the field or in the lab for various assay tests in the next several years.  By 2014, more than 1,000 trees were growing in several field sites.<ref>{{cite web|url=http://www.geneticliteracyproject.org/2015/06/04/government-approval-next-step-in-approving-gm-revival-of-american-chestnut/|title=Government approval next step in GM revival of American chestnut - Genetic Literacy Project|date=2015-06-04|website=www.geneticliteracyproject.org|access-date=9 November 2018}}</ref> Government approval will be required before returning any of these blight resistant trees to the wild.<ref>{{cite web|url=http://theplate.nationalgeographic.com/2015/06/02/can-we-engineer-an-american-chestnut-revival/|archive-url=https://web.archive.org/web/20160722024438/http://theplate.nationalgeographic.com/2015/06/02/can-we-engineer-an-american-chestnut-revival/|url-status=dead|archive-date=July 22, 2016|title=Can We Engineer an American Chestnut Revival?|date=2 June 2015|website=nationalgeographic.com|access-date=9 November 2018}}</ref> The [[New York Botanical Garden]] has planted several of the transgenic trees for public display.<ref>{{cite web|url=http://phenomena.nationalgeographic.com/2013/03/11/resurrecting-a-forest/|archive-url=https://web.archive.org/web/20130314024548/http://phenomena.nationalgeographic.com/2013/03/11/resurrecting-a-forest/|url-status=dead|archive-date=March 14, 2013|title=Resurrecting A Forest|date=11 March 2013|website=nationalgeographic.com|access-date=9 November 2018}}</ref> 
At the start, there were few such engineered chestnut trees. For seed multiplication, [[grafting]] could work.<ref name="Plantopia" /> Normal tree growth requires 6, 7, or even 8 years before a chestnut will flower.<ref name="Plantopia" /> However [[orchard]] management may accelerate pollen production to 2–3 years (although still without fruiting).<ref name="Plantopia" /> Powell's lab had been able to use [[Environmental chamber|growth chamber]]s with higher light inputs to get duration to pollen production down to less than a year.<ref name="Plantopia" />

[[The American Chestnut Foundation]] (TACF) once worked close with SUNY ESF to utilize the [[Darling 58]] in their mission to restore the American chestnut to its native range in the eastern United States.<ref>{{Cite web |title=Darling 58 |url=https://tacf.org/darling-58/ |access-date=2023-08-25 |website=The American Chestnut Foundation |language=en-US}}</ref> However, in December 2023, TACF withdrew its petition for use as a restorative species due to poor performance and high mortality in Darling 54 saplings. <ref>{{Cite web |title=Press Release: TACF Discontinues Development of Darling 58 |url=https://tacf.org/tacf-discontinues-development-of-darling-58/ |access-date=2023-12-08 |website=The American Chestnut Foundation |date=8 December 2023 |language=en-US}}</ref>

==Economic and ecological impact of disease==
In less than fifty years after its emergence, ''C. parasitica'' virtually eliminated American chestnut as a canopy species in {{convert|8.8|e6acre|e6ha}} of forest.<ref name=":4">{{Cite journal|vauthors=Holmes TP, Aukema JE, Von Holle B, Liebhold A, Sills E |date=2009|title=Economic Impacts of Invasive Species in Forest: Past, Present, and Future|journal=Year in Ecology and Conservation Biology |volume=1162 |pages=18–38 |doi=10.1111/j.1749-6632.2009.04446.x |pmid=19432643|s2cid=8965128}}</ref> The chestnut fruit was a major food source for animals in the low elevation Appalachian forests. This loss resulted in a drastic decrease in the squirrel population, the extinction of seven native moth species, and the slowed recovery of deer, Cooper's hawk, cougar, and bobcat populations.<ref name=":5">{{Cite conference |last=Davis|first=Donald |date=May 2006 |title=Historical significance of American chestnut to Appalachian culture and ecology |editor=Kim C. Steiner |editor2=John E. Carlson |book-title=Restoration of American Chestnut to Forest Lands |s2cid=131087587 |url=https://ecosystems.psu.edu/research/chestnut/information/conference-2004/conference}}</ref> The effects of this disease also rippled further through the ecosystem, being linked to a decrease in the abundance of cavity-nesting birds and to a decrease in river water quality which negatively affected aquatic invertebrate populations.<ref name=":4" />

In 1912, standing chestnut timber in just three states was estimated to be $82.5&nbsp;million ($1.9&nbsp;billion in 2009 dollars) in value.<ref name=":4" /> Therefore, in addition to ecological impacts, ''C. parasitica'' potentially caused a devastating loss in economic welfare for communities dependent on the chestnut tree. Mountaineers, residents of Appalachian Mountain communities, had to drastically alter their lifestyles to cope with the effects of this disease.<ref name=":5" />

Economic effects have also been considerable in Europe, particularly before CHV1 spreads naturally to a region. In Greece for example, the disease forced the migration of people who could no longer afford to live off chestnut trees. It has also led to a 40% decline in Greek chestnut production.<ref>{{Cite journal|last=Diamandis|first=S|date=2018|title=Management of Chestnut Blight in Greece Using Hypovirulence and Silvicultural Interventions|doi=10.3390/f9080492|journal=Forests|volume=9|issue=8|page=492|doi-access=free}}</ref>

==See also==
* [[Phytophthora cambivora]]
* [[Phytophthora katsurae]]
* [[American Chestnut Cooperators Foundation]]
* [[Darling 58]]
* [[Forest pathology]]
* [[Lists of invasive species]]
* [[Forest disturbance of invasive insects and diseases in the United States]]
* [[The Weeping Beech]]
*[[Ozark Chinquapin Foundation]]

==References==
{{Reflist|refs=

<ref name="ACF-biocontrol">{{cite web | title=A Brief Summary of Chestnut Canker Biocontrol | website=[[The American Chestnut Foundation]] | date=2019-08-12 | url=http://acf.org/ct/news-and-updates/a-brief-summary-of-chestnut-canker-biocontrol/ | access-date=2021-03-24 | archive-date=2021-12-05 | archive-url=https://web.archive.org/web/20211205004315/https://acf.org/ct/news-and-updates/a-brief-summary-of-chestnut-canker-biocontrol/ | url-status=dead }}</ref>

<ref name="American-chestnut">''American Chestnut: The Life, Death, and Rebirth of a Perfect Tree,'' Susan Freinkel, 2009, p 81</ref>


<ref name=Appalachian-Woods>{{cite web |url=http://www.appalachianwoods.com/appalachianwoods/history_of_the_american_chestnut.htm |title=History of the America Chestnut Tree |archive-url=https://web.archive.org/web/20091129001926/http://www.appalachianwoods.com/appalachianwoods/history_of_the_american_chestnut.htm |archive-date=2009-11-29}}</ref>

<ref name="Blight-resistance">{{Cite journal|url=https://www.acf.org/wp-content/uploads/2016/08/Blight-Resistance.pdf|title=Blight Resistance|last=Rea|first=Glen|date=|journal=Journal of American Chestnut Foundation}}</ref>

<ref name="Chen-et-al-2010">{{cite journal|title=Structure of Oxalacetate Acetylhydrolase, a Virulence Factor of the Chestnut Blight Fungus|first1=Chen|last1=Chen|first2=Qihong|last2=Sun|first3=Buvaneswari|last3=Narayanan|first4=Donald L.|last4=Nuss|first5=Osnat|last5=Herzberg|date=20 August 2010|journal=Journal of Biological Chemistry|volume=285|issue=34|pages=26685–26696|doi=10.1074/jbc.M110.117804|pmid=20558740|pmc=2924111|doi-access=free}}</ref>

<ref name="Chestnut blight">{{Cite web|url=http://plantclinic.cornell.edu/factsheets/chestnutblight.pdf|title=Chestnut Blight: ''Cryphonectria parasitica''|last=Conolly|first=N. Barbara|date=December 2007|website=plantclinic.cornell.edu}}</ref>

<ref name="Chestnut's-Last-Stand">{{cite web|url=http://dnr.wi.gov/wnrmag/html/stories/2002/aug02/chest.htm|title=Chestnut's Last Stand -- Wisconsin Natural Resources magazine -- August 2002|first=Gina|last=Childs|website=dnr.wi.gov|access-date=9 November 2018|archive-date=22 August 2010|archive-url=https://web.archive.org/web/20100822171751/http://www.dnr.wi.gov/wnrmag/html/stories/2002/aug02/chest.htm}}</ref>

<ref name="Columbia">{{cite web|url=http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Cryphonectria_parasitica.htm|title=''Cryphonectria_parasitica''|website=www.columbia.edu|access-date=9 November 2018}}</ref>

<ref name="Cornell-Powell-gluten">{{cite AV media | url=https://youtube.com/E_1493BU2yY?t=2079 | title=William Powell American Chestnut Lecture | website=[[YouTube]] | publisher=The Cornell Alliance for Science, [[Cornell University]] | author=Powell, William | date=Dec 5, 2014 }}{{Dead link|date=August 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

<ref name="dof.virginia.gov">{{cite web|url=http://www.dof.virginia.gov/research/chestnut-amer-hist-rest-in-va.htm|title=American Chestnut - History and Restoration Efforts - Research - Virginia Department of Forestry|website=www.dof.virginia.gov|access-date=9 November 2018|archive-date=25 April 2021|archive-url=https://web.archive.org/web/20210425143648/https://dof.virginia.gov/research/chestnut-amer-hist-rest-in-va.htm|url-status=dead}}</ref>

<ref name=Edlin>{{cite book| title=''Trees, Woods and Man'' | first1=H.L. |last1=Edlin |publisher=New Naturalist |year=1970 |isbn=0-00-213230-3}}</ref>

<ref name="Fisher-et-all 2012">{{cite journal|last1=Fisher|first1=Matthew C.|last2=Henk| first2=Daniel. A.|last3=Briggs|first3=Cheryl J.|last4=Brownstein | first4=John S. | last5=Madoff | first5=Lawrence C. | last6=McCraw | first6=Sarah L | last7=Gurr | first7=Sarah J | title=Emerging fungal threats to animal, plant and ecosystem health|journal=[[Nature (journal)|Nature]]|publisher=[[Nature Research]] | volume=484 | issue=7393 | year=2012|doi=10.1038/nature10947|pages=186–194 |pmid=22498624|pmc=3821985|bibcode=2012Natur.484..186F}} , [[NIH Manuscript Submission|NIHMS]] 514851</ref>

<ref name=Forest-Pathology>{{cite web|url=http://www.forestpathology.org/dis_chestnut.html|title=Chestnut Blight - Forest Pathology|website=Forest Pathology|access-date=8 April 2019}}</ref>

<ref name="Havir-Anagnostakis-1983">{{cite journal | last1=Havir | first1=Evelyn A. | last2=Anagnostakis | first2=Sandra L. | title=Oxalate production by virulent but not by hypovirulent strains of ''Endothia parasitica'' | journal=[[Physiological Plant Pathology]] | publisher=[[Elsevier]] BV | volume=23 | issue=3 | year=1983 | issn=0048-4059 | doi=10.1016/0048-4059(83)90021-8 | pages=369–376}}</ref>

<ref name=Hypovirulence>[http://vatacf.org/hypovirulence.shtml Hypovirulence-Infecting the infection] {{webarchive |url=https://web.archive.org/web/20120227170459/http://vatacf.org/hypovirulence.shtml |date=February 27, 2012 }}</ref>

<ref name="Liang-et-al-2001">{{cite journal | title=Increased ''Septoria musiva'' resistance in transgenic hybrid poplar leaves expressing a wheat oxalate oxidase gene | pmid=11430425 | s2cid=19973881 | last1=Liang | first1=Haiying | last2=Maynard | first2=Charles A. | last3=Allen | first3=Randy D. | last4=Powell | first4=William A. | journal=[[Plant Molecular Biology]] | publisher=[[Springer Science+Business Media|Springer Science and Business Media LLC]] | volume=45 | issue=6 | year=2001 | issn=0167-4412 | doi=10.1023/a:1010631318831 | pages=619–629}}</ref>

<ref name=Milgroom>{{cite journal|vauthors=Milgroom MG, Cortesi P |title=Biological control of chestnut blight with hypovirulence: a critical analysis|journal=[[Annual Review of Phytopathology]] |volume=42 |pages=311–38 |year=2004 |doi=10.1146/annurev.phyto.42.040803.140325 |pmid=15283669}}</ref>

<ref name="Miller">{{Cite journal|last1=Miller|first1=Amy C.|last2=Woeste|first2=Keith E.|last3=Anagnostakis|first3=Sandra L.|last4=Jacobs|first4=Douglass F.|date=2014-01-01|title=Exploration of a rare population of Chinese chestnut in North America: stand dynamics, health and genetic relationships|journal=AoB Plants|language=en|volume=6|doi=10.1093/aobpla/plu065|pmid=25336337|pmc=4243075}}</ref>

<ref name=Missouri-Botanical-Garden>{{Cite web|url=http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/cankers/chestnut-blight.aspx |title=Chestnut Blight |last=Garden |first=Missouri Botanical |website=www.missouribotanicalgarden.org |access-date=2016-11-13}}</ref>

<ref name=Mlinarec-2018>{{Cite journal|last=Mlinarec|first=J|date=2018|title=Molecular evolution and invasion pattern of ''Cryphonectria hypovirus 1'' in Europe: Mutation rate, and selection pressure differ between genome domains.|doi=10.1016/j.virol.2017.11.011|pmid=29179038|journal=Virology|volume=514|pages=156–164|doi-access=}}</ref>

<ref name="Plantopia">{{cite web | last=Gadoury | first=David | title=The New American Chestnut - William Powell | website=Plantopia | date=2020-04-20 | url=http://www.plantopiapodcast.org/2 | access-date=2021-02-26}}</ref>

<ref name="Plantopia-Powell">{{cite web | title=William Powell | website=Plantopia | date=2020-04-20 | url=http://www.plantopiapodcast.org/guests/william-powell | access-date=2021-02-26}}</ref>

<ref name=Rigling>{{Cite journal|last1=Rigling|first1=Daniel|last2=Prospero|first2=Simone|date=2018|title=''Cryphonectria parasitica'', the causal agent of chestnut blight: invasion history, population biology and disease control|url= |journal=Molecular Plant Pathology|language=en|volume=19|issue=1|pages=7–20|doi=10.1111/mpp.12542|issn=1364-3703|pmc=6638123|pmid=28142223}}</ref>

<ref name="Roane-et-al-1986">{{cite book | last1=Roane | first1=Martha K. | last2=Griffin | first2=Gary J. | last3=Elkins | first3=John Rush | title=Chestnut Blight, Other ''Endothia'' Diseases, and the Genus ''Endothia'' | publisher=[[APS Press]], American Phytopathological Society | series=APS monograph series | year=1986 | isbn=978-0-89054-073-2 | url=https://books.google.com/books?id=_KVlQgAACAAJ | access-date=2022-07-02 | pages=vii+53 | s2cid=83360677 | id=[[Invasive Species Compendium|CABI ISC]] [http://www.cabi.org/isc/abstract/19870615566 19870615566]. [[AGRIS]] id [http://agris.fao.org/agris-search/search.do?recordID=US8920239 US8920239] | issn=1051-1113}}</ref>

<ref name=Robin>{{Cite journal|last=Robin |first=C |date=2001 |title=Chestnut blight in Europe: Diversity of ''Cryphonectria parasitica'', hypovirulence and biocontrol |url=https://www.researchgate.net/publication/228746010 |journal=Forest Snow and Landscape Research |volume=76 |number=3 |pages=361–367}}</ref>

<ref name=Salem >Salem Board & Beam {{usurped|1=[https://archive.today/20130104141146/http://www.salemboard.com/furniture/conservation.php American Chestnut Restoration]}}</ref>

<ref name="Sierra-Club-transgenic">{{cite web | title=The Demise and Potential Revival of the American Chestnut | website=Sierra Club | date=2021-02-17 | url=http://www.sierraclub.org/sierra/2021-2-march-april/feature/demise-and-potential-revival-american-chestnut | access-date=2021-02-26}}</ref>

<ref name="Templeton-Powell">Archived at [https://ghostarchive.org/varchive/youtube/20211211/-mhMdUryolU Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20200502092430/https://www.youtube.com/watch?v=-mhMdUryolU Wayback Machine]{{cbignore}}: {{cite AV media|url=https://www.youtube.com/watch?v=-mhMdUryolU|title=The Chestnut Tree: Bringing Back an American Icon {{!}} William Powell|website=[[YouTube]]}}{{cbignore}}</ref>

<ref name="Thys">Thys, Fred [http://www.wbur.org/news/2008/78764_20080718.asp The American Chestnut Returns] for WBUR news. July 18, 2008.</ref>

<ref name="Welch-et-al-2007">{{cite journal | last1=Welch | first1=Andreanna Jo | last2=Stipanovic | first2=Arthur John | last3=Maynard | first3=Charles Alvin | last4=Powell | first4=William Allen | title=The effects of oxalic acid on transgenic ''Castanea dentata'' callus tissue expressing oxalate oxidase | journal=[[Plant Science (journal)|Plant Science]] | publisher=[[Elsevier]] BV | volume=172 | issue=3 | year=2007 | issn=0168-9452 | doi=10.1016/j.plantsci.2006.10.015 | pages=488–496}}</ref>

<ref name="Zhang-et-al-2013">{{cite journal | last1=Zhang | first1=Bo | last2=Oakes | first2=Allison D. | last3=Newhouse | first3=Andrew E. | last4=Baier | first4=Kathleen M. | last5=Maynard | first5=Charles A. | last6=Powell | first6=William A. | title=A threshold level of oxalate oxidase transgene expression reduces ''Cryphonectria parasitica''-induced necrosis in a transgenic American chestnut (''Castanea dentata'') leaf bioassay | journal=[[Transgenic Research]] | publisher=[[Springer Science+Business Media|Springer Science and Business Media LLC]] | volume=22 | issue=5 | date=2013-03-31 | issn=0962-8819 | pmid=23543108 | pmc=3781299 | doi=10.1007/s11248-013-9708-5 | pages=973–982}}</ref>

}}

==Further reading==
*{{cite book | last1=Roane | first1=Martha K. | last2=Griffin | first2=G. J. | last3=Elkins | first3=J. R. | title=Chestnut blight, other ''Endothia'' diseases, and the genus ''Endothia'' | publisher=APS Press, [[American Phytopathological Society]] | publication-place=[[Saint Paul, Minnesota]] | year=1986 | isbn=978-0-89054-073-2 | oclc=14139066 | page=vii+53}}

==External links==
{{Commons category|Cryphonectria parasitica}}
*[http://www.accf-online.org/blight.html American Chestnut Cooperators' Foundation - Blight Fungus]
*[https://www.dontmovefirewood.org/pest_pathogen/chestnut-blight-html/ Don't Move Firewood - Gallery of Pests: Chestnut Blight]
*[http://www.esf.edu/chestnut/ SUNY ESF Chestnut Restoration Project]
*{{usurped|1=[https://archive.today/20130414195252/http://foresthealthinitiative.org/ Forest Health Initiative]}}
*[http://www.tacf.org/ The American Chestnut Foundation]
* [https://www.invasivespeciesinfo.gov/terrestrial/pathogens-and-diseases/chestnut-blight Species Profile - Chestnut Blight (''Cryphonectria parasitica'')], National Invasive Species Information Center, [[United States National Agricultural Library]].

{{Taxonbar|from=Q1010057}}
{{Authority control}}

{{DEFAULTSORT:Chestnut Blight}}
[[Category:Fungal tree pathogens and diseases]]
[[Category:Diaporthales]]
[[Category:Forestry in the United States]]
[[Category:Fungi described in 1906]]
[[Category:Fungi of Asia]]
[[Category:Fungi of Europe]]
[[Category:Taxa named by William Alphonso Murrill]]
[[Category:Castanea|+]]
[[Category:Nut tree diseases]]
[[Category:Fungus species]]