Editing American chestnut (section)

===Ink disease===
{{Main|Phytophthora cinnamomi}}

Before the onset of chestnut blight and prior to 1824, an epidemic of [[Phytophthora cinnamomi|ink disease]] struck American chestnuts, most likely brought to the southern United States on [[Quercus suber|Cork oak]] trees imported from [[Portugal]].<ref>{{cite journal |author=Anagnostakis |first=Sandra L. |date=October 2012 |title=Chestnut Breeding in the United States for Disease and Insect Resistance |journal=Plant Disease |publisher=The American Phytopathological Society |volume=96 |issue=10 |pages=1392–1403 |doi=10.1094/PDIS-04-12-0350-FE |issn=0191-2917 |pmid=30727322 |doi-access=free|bibcode=2012PlDis..96.1392A }}</ref> This fungal pathogen is known to also kill the roots and collars of several ''Castanea'' species, including the European sweet chestnut. It affected primarily chestnuts in the Southeastern US and at the later time when chestnut blight struck, the range of ''C.&nbsp;dentata'' may have already been reduced. The potential range of blight-resistant American chestnuts is substantially reduced if those chestnuts are susceptible to ink disease.<ref>{{cite journal |last1=Gustafson |first1=Eric J. |last2=Miranda |first2=Brian R. |last3=Dreaden |first3=Tyler J. |last4=Pinchot |first4=Cornelia C. |last5=Jacobs |first5=Douglass F. |title=Beyond blight: Phytophthora root rot under climate change limits populations of reintroduced American chestnut |journal=Ecosphere |date=February 2022 |volume=13 |issue=2 |doi=10.1002/ecs2.3917|bibcode=2022Ecosp..13E3917G |s2cid=246665585 }}</ref> Further, the range of this pathogen will extend northward as the climate warms, which may further limit the potential range of the American chestnut.<ref>{{cite journal |last1=Gustafson |first1=Eric J. |last2=Miranda |first2=Brian R. |last3=Dreaden |first3=Tyler J. |last4=Pinchot |first4=Cornelia C. |last5=Jacobs |first5=Douglass F. |title=Beyond blight: Phytophthora root rot under climate change limits populations of reintroduced American chestnut |journal=Ecosphere |date=February 2022 |volume=13 |issue=2 |doi=10.1002/ecs2.3917|bibcode=2022Ecosp..13E3917G }}</ref> Potassium phosphonate has been found to induce resistance to infection of ''C.&nbsp;sativa'' by both inhibiting ''Phytophthora'' species directly and by improving the host response, inducing resistance to lesions in [[phloem]] tissue and formation of callus.<ref>{{cite journal |last1=Brandano |first1=Andrea |last2=Serra |first2=Salvatorica |last3=Hardy |first3=Giles E. St. J. |last4=Scanu |first4=Bruno |title=Potassium Phosphonate Induces Resistance in Sweet Chestnut against Ink Disease Caused by Phytophthora Species |journal=Pathogens |date=22 February 2023 |volume=12 |issue=3 |page=365 |doi=10.3390/pathogens12030365 |pmid=36986287 |pmc=10054612 |doi-access=free }}</ref> Whether or not this effect would occur in ''C.&nbsp;dentata'' is uncertain.<ref>{{cite journal |last1=Vannini |first1=Andrea |last2=Morales-Rodriguez |first2=Carmen |title=Phytophthora diseases |journal=Forest Microbiology |date=2022 |pages=379–402 |doi=10.1016/B978-0-323-85042-1.00016-1|isbn=978-0-323-85042-1 }}</ref>