Date of Graduation

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Plant Science (PhD)

Degree Level

Graduate

Department

Plant Pathology

Advisor/Mentor

Tzanetakis, Ioannis E.

Committee Member

Chen, Pengyin

Second Committee Member

Johnson, Donn T.

Third Committee Member

McDonald, Garry V.

Fourth Committee Member

Rupe, John C.

Keywords

Epidemiology; Resistance; Soybean; Thrips; Transmission; Virus

Abstract

Soybean (Glycine max (L.) Merrill) is one the most important crops in global agriculture with annual production of over 260 million metric tons. As the dependence of a growing global population to soybean has increased, so does the importance of soybean diseases and pests. Over 200 pathogens attack soybean; among them, viruses pose a major threat to the soybean industries accounting for approximately 10% of the annual yield reduction caused by diseases in the past two decades. Soybean vein necrosis virus (SVNV) is a relatively newly discovered virus causing the homonymous disease. The widespread occurrence of the disease in major soybean producing regions in North America and its negative impact on seed quality led to the work presented here; research that aims to better understand virus epidemiology so as to develop effective virus control and disease management tools. In order to further understand the potential roles of weeds in SVNV cycle, surveys were conducted to determine the presence of SVNV among 32 weed species collected from soybean fields in Arkansas. Kudzu (Pueraria montana), a common weed present in millions of acres in Southeastern United States, can sustain SVNV replication in a systemic manner without developing virus-like symptoms. SVNV – a localized virus in soybean, could move systemically with the assistance of bean pod mottle virus, one of the most economically important soybean viruses. The ineffectiveness of pesticides in thrips management highlights the need to identify potential resistance mechanisms to the primary and highly efficient vector of SVNV – Neohydatothrips variabilis (Beach). The comparison of transmission efficiency of thrips fed with polypeptides containing RGD motif and N-linked glycosylation sites of SVNV glycoproteins indicated that blocking putative cellular receptors prior to virus acquisition could significantly reduce the virus transmission efficiency. Due to the lack of resistance to SVNV, efforts were made to identify genotypes with resistance to the vector, which could modify vector behavior and reduce the incidence of transmission and disease. Screening of soybean accessions with differential leaf pubescence levels revealed that feeding damage caused by thrips differs among accessions and is weakly correlated to their pubescence levels.

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