American Elm tree canopy.

MN Impact: Researchers Uncover How Some Elm Cultivars Are More Resistant to DED

January 18, 2019

Objective

Researchers will uncover key chemical and morphological characteristics of trees responsible for their increased resistance to diseases (reported as the number of characteristics discovered).

Issue

Dutch elm disease (DED) remains the most devastating invasive tree disease to affect Minnesota. Despite extensive research on DED, it remains unclear what mechanisms allow certain elms to be resistant while others are susceptible.

What has been done

Five cultivars and two populations of American elm (3 and 4 years old) were examined for differences in their abilities to compartmentalize and resist infection. The trees were assessed multiple times for disease severity on a 1-12 scale, based on the percentage of permanent wilt in their crown and microscopic analyses of the host-parasite interaction.

Results

Cultivars differed in their ability to compartmentalize infection. The two cultivars that most consistently limited the spread of infection by walling off the pathogen enabling the tree to continue to grow were 'Prairie Expedition' and 'Valley Forge'. 'Valley Forge,' in particular, used two mechanisms (1) restricting the spread into newly formed xylem and (2) consistently limiting the tangential spread.

Understanding the characteristics that some cultivars have to resist and limit infection is a key component to assist in the evaluation of other cultivars and could, ultimately, lead to this classic American tree relining our streets.

Additional Resources

UMN Elm Project
UFORE Nursery and Lab
College of Food, Agricultural and Natural Resource Sciences
UMN Extension - Natural Resources