Dissertation
Biological and molecular studies on plant para-retroviruses associated with Dahlia spp. in natural and managed ecosystems
Washington State University
Doctor of Philosophy (PhD), Washington State University
08/2010
DOI:
https://doi.org/10.7273/000006043
Abstract
Three distinct plant para-retroviruses belonging to the genus Caulimovirus were found to be associated with dahlia (Dahlia variabilis): Dahlia mosaic virus (DMV), DMV-D10, and Dahlia common mosaic virus (DCMV). DMV-D10 was the most prevalent (94% of tested samples) followed by DCMV (48.5%) and DMV (23%) in cultivated dahlias during surveys conducted in 2007 and 2008. Biological studies using Verbesina encelioides as the assay plant showed that DMV and DCMV were transmitted by the aphid, Myzus persicae. Mechanical inoculation of V. encelioides showed that DMV and DCMV are transmitted 58% and 36%, respectively. DMV-D10 was not transmissible by either aphids or mechanical inoculation. Selected wild Dahlia species (D. coccinea, D. tenuicaulis, D. rupicola, and D. sherffii) in their natural habitats from west-central Mexico were tested for the three caulimoviruses. Results showed that the wild dahlia species contained only DMV-D10 in 91% of the samples (n=56). The structure and genome organization of DMV-D10 from three wild species, D. coccineav(D10-DC), D. sherffii (D10-DS) and D. tenuicaulis (D10-DT) were determined and compared to that of D10-US (DMV-D10) from cultivated species (D. variabilis). The complete ca. 7 kb dsDNA genomes of D10-DC, D10-DS, and D10-DT had the structure and organization typical of a Caulimovirus species and shared 89.3 to 96.6% amino acid sequence identity among various ORFs when compared to those of D10-US from D. variabilis. DMV-D10 exists as an endogenous plant pararetorviral sequence in cultivated dahlias, contrary to DMV and DCMV which are typical members of the genus Caulimovirus and considered to exist as episomal molecules in infected cells. Genomic Southern hybridization showed differences of integration frequency between different dahlia cultivars. RT-PCR results indicated that both RNA transcripts (35S and 19S) of D10 could be present in infected plants. The importance of these integrated viral sequences in inducing disease and the conditions that influence the induction of expression of the viral genes and symptoms remain to be seen. The discovery of plant para-retroviruses in wild dahlia species in their natural habitats could potentially provide important insights into the possible emergence, co-existence and co-evolution of para-retroviruses and their host plants.
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Details
- Title
- Biological and molecular studies on plant para-retroviruses associated with Dahlia spp. in natural and managed ecosystems
- Creators
- Sahar Eid
- Contributors
- Hanu R. Pappu (Chair)A KARASEV (Committee Member)Amit Dhingra (Committee Member) - Washington State University, Department of HorticultureScot Howard Hulbert (Committee Member) - Washington State University, Department of Plant Pathology
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Plant Pathology
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 130
- Identifiers
- 99901055125801842
- Language
- English
- Resource Type
- Dissertation