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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of 19 American Elm Clones for Tolerance to Dutch Elm Disease

Authors
item Townsend, Alden
item Bentz, Susan
item Douglass, Larry - UNIV. OF MARYLAND

Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 2005
Publication Date: March 1, 2005
Citation: Townsend, A.M., Bentz, S.E., Douglass, L.W. 2005. Evaluation of 19 American elm clones for tolerance to Dutch elm disease. J. Environ. Hort. 23:21-24.

Interpretive Summary: DUTCH ELM DISEASE (DED), CAUSED BY THE FUNGI OPHIOSTOMA ULMI AND OPHIOSTOMA NOVO-ULMI, CONTINUES TO THREATEN NEWLY PLANTED AND ESTABLISHED TREES OF AMERICAN ELM (ULMUS AMERICANA L.). IN THIS STUDY, WE INOCULATED 526 NINE-YEAR-OLD TREES REPRESENTING 19 AMERICAN ELM SELECTIONS AND NAMED CULTIVARS, AMERICAN ELM SEEDLINGS, AND TWO NON-AMERICAN ELM SELECTIONS, TO DETERMINE THEIR RELATIVE DED TOLERANCE. TWO YEARS AFTER INOCULATION, THE AMERICAN ELM CLONES VARIED FROM 0% TO 42% IN AVERAGE CROWN DIEBACK. SEVERAL CULTIVARS AND SELECTIONS SHOWED SUPERIOR DISEASE TOLERANCE. RESULTS WILL BE OF INTEREST TO THOSE NURSERYMEN INTERESTED IN EVALUATING, GROWING, AND SELLING A DIVERSE SELECTION OF AMERICAN ELM CLONES WITH HIGH LEVELS OF TOLERANCE TO DED.

Technical Abstract: ROOTED STEM CUTTINGS OF 19 AMERICAN ELM (ULMUS AMERICANA L.) CULTIVARS AND SELECTIONS, AND ROOTED CUTTINGS OF TWO NON-AMERICAN ELM SELECTIONS, U. CARPINIFOLIA 51 AND 970 (U. GLABRA X (U. WALLICHIANA X U. CARPINIFOLIA)), ALONG WITH A GROUP OF AMERICAN ELM SEEDLINGS, WERE PLANTED IN A RANDOMIZED BLOCK DESIGN. WHEN THE TREES WERE NINE YEARS OLD, THEY WERE INOCULATED WITH A MIXED SPORE SUSPENSION OF OPHIOSTOMA ULMI AND OPHIOSTOMA NOVO-ULMI, THE CAUSAL FUNGI FOR DUTCH ELM DISEASE (DED). ANALYSES OF VARIANCE SHOWED HIGHLY SIGNIFICANT VARIATION AMONG CLONES IN FOLIAR SYMPTOMS 4 WEEKS AFTER INOCULATION AND IN CROWN DIEBACK ONE AND TWO YEARS AFTER INOCULATION. AFTER TWO YEARS, 13 OF THE AMERICAN CLONES SHOWED SIGNIFICANTLY LESS DIEBACK THAN THE AMERICAN ELM SEEDLINGS, AND 18 AMERICAN CLONES SHOWED SIGNIFICANTLY LESS INJURY THAN A RANDOMLY CHOSEN, UNSELECTED AMERICAN ELM CLONE, 57845. THE AMERICAN CLONES WITH THE MOST DED-TOLERANCE WERE CULTIVARS 'VALLEY FORGE,' 'PRINCETON,' 'DELAWARE,' AND 'NEW HARMONY,' AND SELECTIONS N3487, R18-2, 290, 190, AND GDH. THE NON-AMERICAN SELECTIONS 51 AND 970 ALSO EXHIBITED HIGH LEVELS OF DISEASE TOLERANCE. MOST SUSCEPTIBLE WERE AMERICAN CLONES 57845, 'AUGUSTINE,' CRANDALL, W590, AND THE AMERICAN ELM SEEDLINGS. THE MOST DISEASE-TOLERANT AMERICAN ELM SELECTIONS IDENTIFIED IN THIS STUDY ARE BEING EVALUATED FURTHER FOR POSSIBLE NAMING AND RELEASE TO THE NURSERY INDUSTRY.

Last Modified: 4/16/2014
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