Editing Elm (section)

=== Species and species cultivars ===
In North America, careful selection has produced a number of trees resistant not only to DED, but also to the droughts and cold winters that occur on the continent. Research in the United States has concentrated on the American elm (''U. americana''), resulting in the release of DED-resistant clones, notably the [[cultivar]]s [[Ulmus americana 'Valley Forge'|'Valley Forge']] and [[Ulmus americana 'Jefferson'|'Jefferson']]. Much work has also been done into the selection of disease-resistant Asiatic species and cultivars.<ref name="Ware">Ware, G. (1995). Little-known elms from China: landscape tree possibilities. ''[http://www.ces.ncsu.edu/fletcher/programs/nursery/metria/metria8/m87.pdf Journal of Arboriculture] {{webarchive|url=https://web.archive.org/web/20071130221822/http://www.ces.ncsu.edu/fletcher/programs/nursery/metria/metria8/m87.pdf|date=30 November 2007}}'', (November 1995). International Society of Arboriculture, Champaign, Illinois, US.</ref><ref name="Biggerstaffe">Biggerstaffe, C., Iles, J. K., & Gleason, M. L. (1999). ''Sustainable urban landscapes: Dutch elm disease and disease-resistant elms''. SUL-4, Iowa State University</ref>

In 1993, Mariam B. Sticklen and Mark G. Bolyard reported the results of experiments funded by the US [[National Park Service]] and conducted at [[Michigan State University]] in [[East Lansing, Michigan|East Lansing]] that were designed to apply [[genetic engineering techniques]] to the development of DED-resistant strains of American elm trees.<ref>{{cite book|last1=Bolyard|first1=Mark G.|last2=Sticklen|first2=Mariam B.|editor-last1=Sticklen |editor-first1=Mariam B. |chapter-url=https://books.google.com/books?id=avvxBwAAQBAJ&pg=PA171 |chapter=Chapter 13: Strategies for the Production of Disease-Resistant Elms |editor-last2=Sherald |editor-first2=James L.|title=Dutch Elm Disease Research: Cellular and Molecular Approaches |publisher=Springer-Verlag |year=1993 |isbn=9781461568728 |location=New York |pages=171–183 |lccn=93017484 |oclc=851736058 |access-date=26 December 2024|via=[[Google Books]]}}</ref> In 2007, A. E. Newhouse and F. Schrodt of the [[State University of New York College of Environmental Science and Forestry]] in [[Syracuse, New York|Syracuse]] reported that young [[Transgene|transgenic]] American elm trees had shown reduced DED symptoms and normal [[mycorrhiza]]l colonization.<ref>{{cite journal |last1=Newhouse |first1=A. E. |last2=Schrodt |first2=F |last3=Liang |first3=H. |last4=Maynard |first4=C. A. |last5=Powell |first5=W. A. |year=2007 |title=Transgenic American elm shows reduced Dutch elm disease symptoms and normal mycorrhizal colonization |journal=Plant Cell Rep. |volume=26 |pages=977–987 |doi=10.1007/s00299-007-0313-z |pmid=17310333 |number=7 |bibcode=2007PCelR..26..977N |s2cid=21780088}}</ref>

In Europe, the European white elm (''U. laevis'') has received much attention. While this elm has little innate resistance to DED, it is not favoured by the vector bark beetles. Thus it becomes colonized and infected only when no other elms are available, a rare situation in western Europe. Research in Spain has suggested that it may be the presence of a [[triterpene]], [[alnulin]], which makes the tree bark unattractive to the beetle species that spread the disease.<ref name="Martín-Benito">Martín-Benito D., Concepción García-Vallejo M., Pajares J. A., López D. 2005. "[http://pubs.nrc-cnrc.gc.ca/rp/rppdf/x04-158.pdf Triterpenes in elms in Spain] {{webarchive|url=https://web.archive.org/web/20070628155809/http://pubs.nrc-cnrc.gc.ca/rp/rppdf/x04-158.pdf|date=28 June 2007}}". ''Can. J. For. Res.'' 35: 199–205 (2005).</ref> This possibility, though, has not been conclusively proven.<ref name="Pajares">Pajares, J. A., García, S., Díez, J. J., Martín, D. & García-Vallejo, M. C. 2004. "[http://www.revicien.net/abstract.php?ID=1712&Revista=7&PHPSESSID=63aad7e1b38034d0dcce46090b63a5c3 Feeding responses by Scolytus scolytus to twig bark extracts from elms] {{webarchive|url=https://web.archive.org/web/20081007035942/http://www.revicien.net/abstract.php?ID=1712&Revista=7&PHPSESSID=63aad7e1b38034d0dcce46090b63a5c3|date=7 October 2008}}". ''Invest Agrar: Sist Recur For.'' 13: 217–225.</ref> More recently, field elms ''Ulmus minor'' highly resistant to DED have been discovered in Spain, and form the basis of a major breeding programme.<ref name="Martin, a">{{cite journal |last1=Martín |first1=JA |last2=Solla |first2=A |last3=Venturas |first3=M |last4=Collada |first4=C |last5=Domínguez |first5=J |last6=Miranda |first6=E |last7=Fuentes |first7=P |last8=Burón |first8=M |last9=Iglesias |first9=S |last10=Gil |first10=L |date=2015-04-01 |title=Seven Ulmus minor clones tolerant to Ophiostoma novo-ulmi registered as forest reproductive material in Spain |journal=IForest - Biogeosciences and Forestry |publisher=Italian Society of Sivilculture and Forest Ecology (SISEF) |volume=8 |issue=2 |pages=172–180 |doi=10.3832/ifor1224-008 |issn=1971-7458 |doi-access=free}}</ref>