Dissertation
Biological and molecular characterization of Dahlia mosaic caulimovirus
Washington State University
Doctor of Philosophy (PhD), Washington State University
08/2007
DOI:
https://doi.org/10.7273/000005736
Abstract
Dahlia is an economically important ornamental crop in the USA and several countries
around the world. Among the viral diseases that affect dahlia, Dahlia mosaic virus (DMV), is
considered to be the most widespread and to have the greatest impact on flower production.
Molecular characterization of DMV showed the association of two distinct caulimoviruses
(DMV-D10, DMV-Portland) and a D10-like sequence variant (DMV-Holland) with the disease.
The genome structure and organization of DMV-D10 was determined. The double stranded
DNA genome shared many features with the members of the genus Caulimovirus. However,
sequence identity of various open reading frames of DMV-D10 with known caulimoviruses
ranged from 32-70% at amino acid level suggesting that D10 is a distinct caulimovirus.
Moreover, the aphid transmission factor was absent and the coat protein was smaller than that
found in other Caulimovirus species. Phylogenetic analysis using amino acid sequences from the
different protein coding regions indicated that DMV-D10 is closely related to DMV-Portland and
Figwort mosaic virus.
A PCR-based assay was used to determine the relative incidence of DMV-D10, DMVPortland
and DMV-Holland in dahlia samples from the USA and the Netherlands. Results indicated that DMV-D10 was present in 87.4% of samples from the USA and 97.6% of the
samples from the Netherlands. Furthermore, 97.6% of samples from the Netherlands were
positive for DMV-Holland while only 31.9% of the samples from the USA were positive. The
presence of DMV-Portland in samples from both the USA and the Netherlands was
comparatively less. The presence of all three DMV sequences in 36.6% of the dahlia samples
from the Netherlands and 6.7% of the dahlia samples from the USA highlighted the importance
of testing for all three sequences for DMV diagnostics. The distribution of DMV in the dahlia
seed was determined by PCR. The viral genome was detected in cotyledons. Seedlings from
grow-out tests were also positive for DMV-D10 indicating that the virus is seed transmitted. The
virus was also detected in the pollen collected from infected plants.
Viruses in certain genera in family Caulimoviridae were shown to integrate their genomic
sequences into their host genomes and exist as endogenous pararetroviral sequences. However,
members of the genus Caulimovirus remained to be an exception and are believed to exist only
as episomal elements during virus infection cycle. Using DMV-D10 specific probes, Southern
blot hybridization of total plant DNA from dahlia seedlings showed the presence of viral DNA in
the host DNA whereas, viral DNA was not detected in other known hosts of DMV. This is the
first report of natural integration of a caulimovirus genome into its host and existence of a
caulimovirus species as an endogenous pararetroviral sequence in a host plant. Epidemiological
and molecular properties of DMV-D10 would facilitate devising management options for
reducing the impact of the virus.
Metrics
2 File views/ downloads
18 Record Views
Details
- Title
- Biological and molecular characterization of Dahlia mosaic caulimovirus
- Creators
- Vihanga Pahalawatta
- Contributors
- Hanu Pappu (Chair) - Washington State University, Department of Plant PathologyPATRICIA OKUBARA (Committee Member)KENNETH C EASTWELL (Committee Member)Gary A Chastagner (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
- 110
- Identifiers
- 99901054763001842
- Language
- English
- Resource Type
- Dissertation