Date of Graduation

12-2020

Document Type

Thesis

Degree Name

Master of Science in Plant Pathology (MS)

Degree Level

Graduate

Department

Entomology and Plant Pathology

Advisor/Mentor

Tzanetakis, Ioannis E.

Committee Member

McDonald, Garry V.

Second Committee Member

Kirkpatrick, Terrence L.

Keywords

Peony; Plant pathology; Plant viruses; Population genetics

Abstract

Peony (Peonia lactiflora, Pall.) is a popular ornamental that has been cultivated for millennia. Due to its popularity, plant material is frequently moved across international borders allowing for the spread of viruses. The virome of several peony plants was investigated and four viruses; namely Amazon lily mild mottle virus (ALiMMV), Cycas necrotic stunt virus (CNSV), Gentian Kobu-sho associated virus (GKaV) and Lychnis mottle virus (LycMoV) were detected for the first time in the Western Hemisphere. Incidence ranged from a few plants for ALiMMV to near universal infection for CNSV. GKaV was found in individuals that were infected with Lemoine’s disease of peonies, a disorder causing root galls, and was absent from asymptomatic individuals. Yet more plants affected must be assessed to determine association between virus and disease. CNSV and LycMoV were the most prevalent viruses detected, the majority of the times in asymptomatic infections. High throughput sequencing was employed to examine the population structure of LycMoV and CNSV. Both viruses have homogenous populations in peony and phylogenetic analyses indicate that those isolates form distinct clades. The main evolutionary force identified was negative selection although there were few amino acid positions in CNSV that undergo positive selection. An accurate, multiplex-diagnostic method was developed for CNSV that can detect all published isolates, a valuable tool given that CNSV is known to infect and cause disease in many agricultural and horticultural crops.

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