Thesis
Genetic diversity in viruses associated with apple green crinkle disease (AGCD)
Washington State University
Master of Science (MS), Washington State University
2012
Handle:
https://hdl.handle.net/2376/101419
Abstract
Apple green crinkle disease (AGCD) is widespread in apple orchards worldwide, causing symptoms such as deformation and cracking of fruit. However, these clearly visible symptoms of the disease are only apparent in years with cooler spring temperatures. The mode of spread of AGCD suggests that a viral pathogen might be involved in the etiology. In previous studies, Apple stem pitting virus (ASPV), Apple stem grooving virus (ASGV) and Apple chlorotic leaf spot virus (ACLSV) were detected in diseased trees. This research evaluated the genetic diversity of viruses associated with this disease. Shoots from AGCD-symptomatic and asymptomatic trees were obtained during the summer of 2010 and 2011 from North Carolina (NC) and Washington State (WA), and all samples were indexed for the presence of Apple mosaic virus (ApMV), ACLSV, ASGV, ASPV, viroids in the genus Apscaviroid and phytoplasmas. Results from these analyses demonstrated that ACLSV, ApMV, viroids and phytoplasmas were not associated with AGCD. All samples (n= 13) from commercial orchards in NC and WA (both symptomatic and asymptomatic) that were evaluated in this study tested positive by reverse transcription polymerase chain reaction with primers for ACLSV, ASGV and ASPV, whereas two symptomatic samples that had previously undergone heat therapy yielded positive results for ASGV and ASPV only. Genetic diversity analysis of the coat protein (CP), replicase and triple gene block (TGBs) sequences related to ASPV and ASGV were studied from trees affected and unaffected by AGCD. Sequences of ASGV were genetically conserved in both AGCD-symptomatic and asymptomatic trees; however, ASPV-like sequences were highly variable. Phylogenetic analysis of CP sequences of the ASPV-like revealed six major groups of variants, with two of the six phylogroups comprised only sequences from AGCD-symptomatic trees. Two phylogroups may represent new virus species in the genus Foveavirus. These results point to the possible involvement of one or more of the ASPV-like viruses, with or without ASGV, in the etiology of AGCD, and will direct future efforts to identify and characterize putative causal agent(s) of AGCD in symptomatic apple fruits.
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Details
- Title
- Genetic diversity in viruses associated with apple green crinkle disease (AGCD)
- Creators
- Segun Akinwumi Akinbade
- Contributors
- Kenneth C. Eastwell (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Plant Pathology, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525094401842
- Language
- English
- Resource Type
- Thesis