Intraspecific variability of Geosmithia morbida the causal agent of thousand cankers disease, and effects of temperature, isolate and host family (Juglans nigra) on canker development
Date
2012
Authors
Freeland, Emily, author
Tisserat, Ned, advisor
Leach, Jan, committee member
Cranshaw, Whitney, committee member
Klett, James, committee member
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Abstract
Since the mid-1990's widespread mortality of Black Walnut (Juglans nigra) in the western United States has been noted. This mortality is the result of aggressive feeding of the Walnut twig beetle (Pityophthorus juglandis) and subsequent canker development caused by the newly named fungus Geosmithia morbida. Thousand Canker Disease (TCD) has been confirmed in Oregon, Washington, Idaho, Utah, California, Colorado, New Mexico, Arizona and recently in the native range of J. nigra, in Tennessee, Pennsylvania, and Virginia. Intraspecific variability of isolates was determined using rDNA ITS partial sequences and partial beta tubulin sequences. Nested clade phylogeographic analysis was used to look for correlations between haplotype trees and geography of isolates collected in screenings for the disease. Patterns of restricted dispersal by distance were found for both markers and high variability was found in isolates from single locations. Indicating that the populations causing disease throughout the western United States are not the result of recent point introductions. G. morbida isolate and J. nigra family had inconsistent effects on canker development, while temperature had a consistent effect. At higher temperatures (32°C) canker development was reduced compared to 25°C. Several genetically different G. morbida isolates were compared and repeated differences in pathogenicity were produced.
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Subject
canker development
Juglans nigra
intraspecific variability
Geosmithia morbida