Announcement of Final Thesis Defense Plant Pathology PhD: Ross Hatlan

April 7, 2025 1:30PM - 2:30PM

PSSB 271 Conference Room

"HOPPORTUNITY KNOCKS: MANAGEMENT, DIAGNOSTICS, GENOMICS, AND POPULATION GENETICS OF DIAPORTHE HUMULICOLA"

Members of the Examining Committee and their Department:

  1. Dr. Timothy Miles - Plant, Soil and Microbial Sciences
  1. Dr. Martin Chilvers - Plant, Soil and Microbial Sciences
  1. Dr. Daniel Chitwood - Horticulture
  1. Dr. Mary Hausbeck - Plant, Soil and Microbial Sciences

 

ABSTRACT

 

Diaporthe humulicola is a pathogen of hops, responsible for the disease halo blight. The pathogen was first described in 2020, though it was initially discovered in 2015. It is particularly relevant in the eastern United States and Canada, where it can cause up to 56% yield loss if left untreated. The pathogen produces lesions on leaves surrounded by a chlorotic halo and desiccates the hop cone, leading to shattering during harvest. This dissertation explores various aspects of D. humulicola, including its detection, genetic diversity, and management. Multiple fungicide products were tested to determine effective strategies for controlling the disease. Additionally, a qPCR tool was developed for the detection of D. humulicola in different plant materials. A genome was assembled, and a population genetics study was conducted using isolates from the eastern United States and Canada. Results indicate that fungicides in FRAC groups 3, 7, and 11 can significantly reduce the severity and incidence of halo blight. The developed diagnostic tool is capable of detecting as little as 0.1 picogram of D. humulicola DNA. An annotated genome for the pathogen has been produced and deposited to NCBI. Finally, population genetics analyses suggest that genetic diversity in D. humulicola may be driven by geographic location. The findings of this dissertation provide a foundation for understanding D. humulicola, offering new insights into its detection, genetic diversity, and management strategies.

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