Announcement of Final Thesis Defense Plant Pathology Ph.D. Degree : Rebecca Harkness
April 14, 2025 1:30PM - 2:30PM
The biology of caliciopsis canker disease on North American pines
Members of the Examining Committee and their Department:
- Timothy Miles, Plant, Soil and Microbial Sciences
- Martin Chilvers, Plant, Soil and Microbial Sciences
- Gregory Bonito, Plant, Soil and Microbial Sciences
- James Jacobs, USDA Forest Service, Forest Health Protection
ABSTRACT
Caliciopsis canker disease, caused by the ascomycete fungus Caliciopsis pinea, poses a growing threat to eastern white pine across North America. Infections lead to cankers, reduced tree health, and economic losses. Despite increasing outbreaks, the pathogen's biology and spread remain poorly understood, further inhibited by its morphological similarity to related species. This dissertation focuses on developing improved diagnostic resources for conifer-infecting Caliciopsis species, explores the diversity within the genus, and investigates the epidemiology of C. pinea. First, a comprehensive guide to diagnosing conifer-infecting Caliciopsis species is presented, reviewing microscopic and molecular techniques for laboratory studies. This is followed by a phylogenetic analysis using multiple genes, revealing three new Caliciopsis species in Michigan. Morphological and molecular data strongly support these findings, demonstrating distinct characteristics in mazaedia, locule, and ascospore sizes. Additionally, a highly sensitive and specific qPCR assay targeting the ITS region of C. pinea was developed. This assay overcomes limitations in current diagnostics, enabling accurate detection, quantification, and diagnosis where previously no accurate molecular tools existed. This assay was then used to quantify C. pinea spores from air samples to determine the environmental variables that influence inoculum availability in the air to improve our understanding of the mechanisms of disease spread. Through this research we were able to explore the diversity and biology of C. pinea to compliment the disease mitigation efforts of state and federal forest health entities.
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