Editing Elm (section)

=== Hybrid cultivars ===
Owing to their innate resistance to DED, Asiatic species have been crossed with European species, or with other Asiatic elms, to produce trees that are both highly resistant to disease and tolerant of native climates. After a number of false dawns in the 1970s, this approach has produced a range of reliable hybrid cultivars now commercially available in North America and Europe.<ref>{{cite web |title=Scientific Name: Ulmus x species |url=http://www.hort.cornell.edu/uhi/outreach/recurbtree/pdfs/08Ulmus%20x.pdf |archive-url=https://web.archive.org/web/20081217195926/http://www.hort.cornell.edu/uhi/outreach/recurbtree/pdfs/08Ulmus%20x.pdf |archive-date=17 December 2008 |access-date=26 May 2018}}</ref><ref name="Santini2004">Santini A., Fagnani A., Ferrini F., Mittempergher L., Brunetti M., Crivellaro A., Macchioni N., "[http://www.inia.es/gcontrec/pub/179-184-(15)-Elm_breeding_1161943564468.pdf Elm breeding for DED resistance, the Italian clones and their wood properties] {{webarchive|url=https://web.archive.org/web/20071026213739/http://www.inia.es/gcontrec/pub/179-184-%2815%29-Elm_breeding_1161943564468.pdf|date=26 October 2007}}". ''Invest Agrar: Sist. Recur. For'' (2004) 13 (1), 179–184. 2004.</ref><ref name="Santamour">Santamour, J., Frank, S. & Bentz, S. (1995). Updated checklist of elm (Ulmus) cultivars for use in North America. ''Journal of Arboriculture'', 21:3 (May 1995), 121–131. International Society of Arboriculture, Champaign, Illinois, US</ref><ref name="Smalley">Smalley, E. B. & Guries, R. P. (1993). Breeding Elms for Resistance to Dutch Elm Disease. ''Annual Review of Phytopathology'' Vol. 31 : 325–354. Palo Alto, California</ref><ref name="Heybroeka">{{cite journal |last=Heybroek |first=Hans M. |date=1983 |editor-last=Burdekin |editor-first=D.A. |title=Resistant elms for Europe |url=http://www.forestry.gov.uk/pdf/FCBU060.pdf/$FILE/FCBU060.pdf#page=118 |url-status=live |journal=Forestry Commission Bulletin (Research on Dutch Elm Disease in Europe) |location=London |publisher=HMSO |pages=108–113 |archive-url=https://web.archive.org/web/20170215025124/http://www.forestry.gov.uk/pdf/FCBU060.pdf/$FILE/FCBU060.pdf#page=118 |archive-date=15 February 2017 |number=60 |df=dmy-all}}</ref><ref name="Heybroekb">{{cite book |last1=Heybroek |first1=H.M. |title=Dutch Elm Disease Research |date=1993 |publisher=Springer-Verlag |isbn=978-1-4615-6874-2 |editor1-last=Sticklen |editor1-first=Mariam B. |location=New York, USA |pages=16–25 |chapter=The Dutch Elm Breeding Program |access-date=26 October 2017 |editor2-last=Sherald |editor2-first=James L. |chapter-url=https://books.google.com/books?id=avvxBwAAQBAJ&pg=PA16 |archive-url=https://web.archive.org/web/20171026164004/https://books.google.co.uk/books?id=avvxBwAAQBAJ&pg=PA16&lpg=PA16 |archive-date=26 October 2017 |url-status=live |df=dmy-all}}</ref><ref name="Mittempergher2004">{{cite journal |last1=Mittempergher |first1=L |last2=Santini |first2=A |date=2004 |title=The history of elm breeding |url=http://www.inia.es/gcontrec/Pub/161-177-(14)-The_history_1161943529015.pdf |url-status=live |journal=Investigacion Agraria: Sistemas y Recursos Forestales |volume=13 |issue=1 |pages=161–177 |archive-url=https://web.archive.org/web/20170211155148/http://www.inia.es/gcontrec/Pub/161-177-(14)-The_history_1161943529015.pdf |archive-date=11 February 2017 |df=dmy-all}}</ref> Disease resistance is invariably carried by the female parent.<ref name="Martin, b">Martin, J., Sobrina-Plata, J., Rodriguez-Calcerrada, J., Collada, C., and Gil, L. (2018). Breeding and scientific advances in the fight against Dutch elm disease: Will they allow the use of elms in forest restoration? ''New Forests'', 1-33. Springer Nature 2018. [https://doi.org/10.1007/s11056-018-9640-x]</ref>

Some of these cultivars, notably those with the Siberian elm (''[[Ulmus pumila]]'') in their ancestry, lack the forms for which the iconic American elm and English elm were prized. Moreover, several exported to northwestern Europe have proven unsuited to the [[maritime climate]] conditions there, notably because of their intolerance of anoxic conditions resulting from ponding on poorly drained soils in winter. Dutch hybridizations invariably included the Himalayan elm (''[[Ulmus wallichiana]]'') as a source of antifungal genes and have proven more tolerant of wet ground; they should also ultimately reach a greater size. However, the susceptibility of the cultivar 'Lobel', used as a control in Italian trials, to [[elm yellows]] has now (2014) raised a question mark over all the Dutch clones.<ref name="Mittempergher2000">Mittempergher, L., (2000). Elm Yellows in Europe. In: ''The Elms, Conservation and Disease Management.'' pp.
103-119. Dunn C.P., ed. Kluwer Academic Press Publishers, Boston, USA.</ref>

Several highly resistant ''Ulmus'' cultivars have been released since 2000 by the Institute of Plant Protection in Florence, most commonly featuring crosses of the Dutch cultivar [[Ulmus 'Plantyn'|'Plantijn']] with the Siberian elm to produce resistant trees better adapted to the Mediterranean climate.<ref name="Santini2004" />

====Cautions regarding novel cultivars====
Elms take many decades to grow to maturity, and as the introduction of these disease-resistant cultivars is relatively recent, their long-term performance and ultimate size and form cannot be predicted with certainty. The [[National Elm Trial]] in North America, begun in 2005, is a nationwide trial to assess strengths and weaknesses of the 19 leading cultivars raised in the US over a 10-year period; European cultivars have been excluded.<ref>(1) {{cite web |year=2018 |title=National Elm Trial |url=http://bspm.agsci.colostate.edu/national-elm-trial/ |work=Bioagricultural Sciences & Pest Management |publisher=[[Colorado State University College of Agricultural Sciences]]: [[Colorado State University College of Agricultural Sciences#Academic Departments|Department of Agricultural Biology]] |location=[[Fort Collins, Colorado]] |access-date=8 February 2021 |archive-date=30 March 2018 |archive-url=https://web.archive.org/web/20180330152322/http://bspm.agsci.colostate.edu/national-elm-trial/ |url-status=dead }}.<br />(2) {{cite journal |last1=Griffin |first1=Jason J. |last2=Jacobi, E. |first2=William R. |last3=McPherson |first3=Gregory |last4=Sadof |first4=Clifford S. |last5=McKenna |first5=James R. |last6=Gleason |first6=Mark L. |last7=Gauthier |first7=Nicole Ward |last8=Potter |first8=Daniel A. |last9=Smitley |first9=David R. |last10=Adams |first10=Gerard C. |last11=Gould |first11=Ann Brooks |display-authors=4 |year=2017 |title=Ten-Year Performance of the United States National Elm Trial |url=https://webdoc.agsci.colostate.edu/bspm/NationalElmTrial/AUF2017.pdf |journal=Arboriculture & Urban Forestry |publisher=[[International Society of Arboriculture]] |volume=43 |pages=107–120 |doi=10.17660/ActaHortic.2018.1191.5 |issn=0567-7572 |oclc=7347020445 |access-date=February 7, 2021 |first12=Christian R. |last12=Cash |first13=James A. |last13=Walla |first14=Mark C. |last14=Starrett |first15=Gary |last15=Chastagner |first16=Jeff L. |last16=Sibley |first17=Vera A. |last17=Krischik |first18=Adam F. |last18=Newby |number=3 }}</ref> Meanwhile, in Europe, American and European cultivars are being assessed in field trials started in 2000 by the UK charity [[Butterfly Conservation]].<ref name="Brookes">Brookes, A. H. (2013). ''Disease-resistant elm cultivars, Butterfly Conservation trials report, 2nd revision, 2013.'' Butterfly Conservation, Hants & IoW Branch, England. {{cite web |title=Archived copy |url=http://www.hantsiow-butterflies.org.uk/conservation/2013%20Elm%20Report%20Sept%202013.pdf |url-status=dead |archive-url=https://web.archive.org/web/20140529181302/http://hantsiow-butterflies.org.uk/conservation/2013%20Elm%20Report%20Sept%202013.pdf |archive-date=29 May 2014 |access-date=2014-01-30 |df=dmy-all}}</ref>