Date of Award

8-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant and Environmental Science

Committee Chair/Advisor

Elizabeth J. Cieniewicz

Committee Member

Juan Carlos Melgar

Committee Member

Ksenija Gasic

Committee Member

Lucas Boatwright

Abstract

Blackberry production is growing in popularity in the southeastern U.S. However, blackberry growers in this region report major problems with productivity and longevity due to viruses. First, the state of knowledge on blackberry yellow vein disease (BVYD) complex, associated with mixed infections of a diverse group of viruses, is discussed. Specific viruses associated with symptom types are unknown. Therefore, the etiology of BYVD is not fully understood, which makes BYVD diagnosis challenging. My research focused on improving BYVD diagnosis, etiology, and epidemiology. Second, I developed a farm-level diagnostic protocol to improve virus disease surveillance. High throughput sequencing detected 17 known viruses in the pooled samples, including 11 viruses known to infect blackberry. Third, I investigated the ecology of nine blackberry viruses using a bipartite network analysis approach. More mixed virus infections were detected in the symptomatic and wild plants compared to the asymptomatic plants. Virus accumulation in older plants was significantly higher compared to the virus accumulation observed in younger plantings. This analysis also showed that some cultivars, e.g., ‘Navaho’, harbored more viruses than others. However, no specific virus or virus combination is associated with specific symptomatology, except for oak leaf pattern, which may be associated with three specific viruses. Fourth, I assessed the ingress of five viruses in two new blackberry plantings to evaluate within-season and across-season spread. Virus incidence was low in both sites during the two years of this study, but secondary spread was observed for two viruses, blackberry line pattern virus (BlaLPV) and blackberry virus E (BVE). This study marks the beginning of a long-term epidemiology study, which will provide a better understanding of virus spread mechanisms in the field. Lastly, I discuss the progress made based my dissertation research, synthesize conclusions in the context of virus disease management, and provide some potential future research directions.

Author ORCID Identifier

0009-0002-1932-290X

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