Ulmus americana 'Jefferson'

The American Elm cultivar Ulmus americana 'Jefferson' was cloned from a tree growing near a path in front of the Freer Gallery of Art, close to the Smithsonian Institution Building ("The Castle") on the National Mall in Washington, D.C.[1] The United States National Park Service, which had planted the tree during the 1930s, cloned it in 1993 after screening tests showed that it possessed an outstanding level of tolerance to Dutch elm disease (DED).[1]

Ulmus americana 'Jefferson'
The original 'Jefferson' elm on the National Mall in Washington, D.C. (March 2014)
SpeciesUlmus americana
Cultivar'Jefferson'
OriginNational Park Service, US

In 2005, the Park Service and the Agricultural Research Service (ARS) of the United States Department of Agriculture jointly released the clone (formerly NPS 3-487) to the nursery trade as 'Jefferson'.[1] The parent tree appears to have remained unscathed by DED in 2014.


Description

'Jefferson' is distinguished by its low, spreading form with arching limbs and broad U-shaped crotches.[2] The parent tree on the National Mall has reached a height of about 68 feet (20.7 m) after 80 years. Ploidy: 2n = 42.

Genetics

Early studies on the parent tree found that the tree has triploid chromosomes, suggesting that it may be a hybrid between the tetraploid American Elm and an unknown diploid species.[3] A genetic study that the ARS conducted on the clone at the United States National Arboretum in Washington, D. C., during 2004 confirmed the tree as Ulmus americana, despite having some atypical features.[4]

A subsequent ARS study also confirmed that the tree is a triploid. The study's investigators concluded that a crossing of two American Elms, one a tetraploid, the other a less common diploid, had created the tree. The investigators found no triploids among the 81 wild trees that they sampled.[5]

Pests and diseases

The tree proved highly resistant to Dutch elm disease in an ARS trial (as clone N 3487/NA 62001).[6] NA 62001 showed little damage from elm leaf beetle (Xanthogaleruca luteola) feeding during a 2009—2010 survey at an Oklahoma arboretum.[7] 'Jefferson' is susceptible to elm yellows phytoplasma infection, as are other U. americana DED-resistant cultivars and native trees of that species.[8]

The Japanese beetle (Popillia japonica) highly prefers U. americana when feeding.[9] Verticillium wilt had a greater effect on U. americana than it had on all other elms studied in an investigation of that fungal disease.[10]

Cultivation
President George W. Bush planting a 'Jefferson' clone outside of the White House in October 2006.

'Jefferson' has not been widely tested beyond Washington D.C., although the National Elm Trial that Colorado State University is coordinating is presently evaluating it. The Golden Hill Nursery in Kent introduced 'Jefferson' to the United Kingdom in 2010, but the clone remains rare in cultivation.

Accessions

North America

Europe

Notes
  1. (1) Flores, Alberto (June 13, 2006). "Jefferson Trees Resistant to Dutch Elm Disease". News & Events. United States Department of Agriculture: Agricultural Research Service. Retrieved January 30, 2021. In 2005, the newest American elm—named Jefferson—was released jointly by ARS and the National Park Service (NPS), after collaborative screening tests by Townsend and James L. Sherald, NPS Natural Resource Officer, showed it to have an outstanding level of Dutch elm disease (DED) tolerance. It was cloned in 1993 from the original tree, a survivor of about 300 elms planted on the National Mall in Southwest Washington in the 1930s. Archived January 26, 2021, at the Wayback Machine.
    (2) Bentz, S.E. (February 2005). "Mature American elm of variety "Jefferson," at the old Smithsonian building, Washington, DC" (photograph). Retrieved January 30, 2021 – via elmpost.org. Archived February 2, 2017, at the Wayback Machine.
    (3) Sherald, 2009, pp. 37—38.
  2. Sherald, 2009, p. 38. Photographs: (1) Figure 33: "American elm 'Jefferson'. Parent tree on the National Mall in front of the Freer Gallery of Art on Jefferson Drive, flanked on either side by trees vegetatively propagated from it."
    (2) Figure 34: "Young ‘Jefferson’ elms on the National Mall come into full leaf before native American elms."
  3. (1) Sherald, James L.; Santamour Jr., Frank S.; Hajela, Ravindra K.; Hajela, Neerja; Sticklen, Mariam B. (April 1, 1994). "A Dutch elm disease resistant triploid elm". Canadian Journal of Forest Research. Ottawa, Ontario: Canadian Science Publishing. doi:10.1139/x94-087. ISSN 1208-6037. LCCN 71618428. OCLC 969764715. Retrieved January 30, 2021.
    (2) Warren, Keith (August 21, 2000). "American Elm Cultivars - Ulmus americana: Ulmus americana 'Jefferson': Jefferson Elm". Return of the Elm: The Status of Elms in the Nursery Industry in 2000. J. Frank Schmidt & Son Co. Archived from the original on April 13, 2003 – via North Carolina State University: Mountain Horticultural Crops Research and Extension Center. Triploid. May be a hybrid between tetraploid U. americana and an unknown diploid species.
  4. Pooler, Margaret R.; Townsend, A. M. (September 2005). "Research Reports: DNA Fingerprinting of Clones and Hybrids of American Elm and Other Elm Species with AFLP Markers" (PDF). Journal of Environmental Horticulture. Washington, D.C.: Horticultural Research Institute (HRI), the AmericanHort Foundation. 23 (3): 113–117. doi:10.24266/0738-2898-23.3.113. ISSN 0738-2898. LCCN 83643944. OCLC 1057932522. Retrieved January 30, 2021 – via elmpost.org. (Jefferson's) identity has been questioned due to its disease tolerance, broad U-shaped branch unions, and bark, branch, and leaf characteristics. Archived May 8, 2018, at the Wayback Machine.
  5. (1) Kaplan, Kim (March 30, 2011). "Hidden elm population may hold genes to combat Dutch elm disease". Research News. United States Department of Agriculture: Agricultural Research Service. Retrieved January 30, 2021. To settle the question, the two scientists tested elm trees from across the species' eastern and central U.S. range. About 21 percent of the wild elms sampled were diploid; some grew in stands with tetraploids, while others were larger groupings of diploids. Archived April 6, 2019, at the Wayback Machine.
    (2) Whittemore, Alan T.; Olsen, Richard T. (April 1, 2011). "Ulmus americana (Ulmaceae) is a polyploid complex". American Journal of Botany. St. Louis: Botanical Society of America. 98 (4): 754–760. doi:10.3732/ajb.1000372. ISSN 0002-9122. JSTOR 41149435. LCCN 17005518. OCLC 937099651. PMID 21613171. Retrieved January 30, 2021. The two ploidy levels grew in proximity to one another at several sites, east of the Appalachians and in eastern Missouri and west-central Oklahoma. Despite finding diploid and tetraploid trees growing near each other in several areas, no wild triploids were encountered.
  6. Townsend, A. M.; Bentz, S. E.; Douglass, L. W. (March 2005). "Evaluation of 19 American Elm Clones for Tolerance to Dutch Elm Disease" (PDF). Journal of Environmental Horticulture. Washington, D.C.: Horticultural Research Institute (HRI), the AmericanHort Foundation. 23 (1): 21–24. doi:10.24266/0738-2898-23.1.21. ISSN 0738-2898. LCCN 83643944. OCLC 1057932522 – via elmpost.org. Archived May 11, 2005, at the Wayback Machine.
  7. "Elm Leaf Beetle Survey". Clinton, Oklahoma: Sunshine Nursery & Arboretum. Archived from the original on July 19, 2011. Retrieved July 17, 2017.
  8. (1) Sinclair, W. A.; Townsend, A..M.; Sherald, J. L. (May 2001). Karasev, Alexander V. (ed.). "Elm Yellows Phytoplasma Lethal to Dutch Elm Disease-Resistant Ulmus americana Cultivars". Plant Disease. St. Paul, Minnesota: American Phytopathological Society. 85 (5): 560. doi:10.1094/PDIS.2001.85.5.560B. ISSN 0191-2917. LCCN 79643690. OCLC 819181727. PMID 30823144. Retrieved February 1, 2021 – via PubMed.gov. Archived 2021-02-01 at the Wayback Machine.
    (2) "Elm yellows (Candidatus Phytoplasma ulmi)". Forest Research. England: Forestry Commission. 2020. Infection can be very destructive to some elms, particularly North American species. However, it is thought that European elm species tend to be much less affected than the highly susceptible American elm (U. americana). Archived December 2, 2020, at the Wayback Machine.
  9. Miller, Fredric; Ware, George; Jackson, Jennifer (April 1, 2001). "Preference of Temperate Chinese Elms (Ulmus spp.) for the Adult Japanese Beetle (Coleoptera: Scarabaeidae)". Journal of Economic Entomology. Oxford University Press (OUP). 94 (2): 445–448. doi:10.1603/0022-0493-94.2.445. ISSN 0022-0493. LCCN 11008063. OCLC 1131914636. PMID 11332837.
  10. Pegg, G. F.; Brady, B. L. (2002). Verticillium Wilts. Wallingford, Oxon, UK: CABI Publishing. p. 291. ISBN 0-85199-529-2. LCCN 2001037313. OCLC 290478616 – via Google Books.

References
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.