Dissertation
Molecular Biology and Epidemiology of Grapevine Leafroll-Associated Viruses
Doctor of Philosophy (PhD), Washington State University
01/2016
Handle:
https://hdl.handle.net/2376/12097
Abstract
Studies were conducted on molecular biology and epidemiology of grapevine leafroll-associated viruses infecting wine grape (Vitis vinifera) cultivars in Washington State. In the first objective, the complete genome sequence of two isolates of Grapevine leafroll-associated virus 1 (GLRaV-1, genus: Ampelovirus, family Closteroviridae) was determined to be 18,731 and 18,946 nucleotides. The genome of GLRaV-1 isolates contain nine open reading frames with long 5’ and 3’ non-translated regions (NTRs). The sequence differences in the 5’NTR was used to develop a restriction fragment length polymorphism assay for distinguishing GLRaV-1 variants in vineyards. Northern blot hybridization revealed the presence of three of the eight putative 3' co-terminal subgenomic (sg) RNAs at higher levels in virus infected grapevine samples. The 5’ termini of five sgRNAs were mapped and their leader sequences determined. The results provided a foundation to further elucidate the comparative molecular biology of grapevine-infecting members of the family Closteroviridae.
In the second objective, the spread of grapevine leafroll disease (GLD) was monitored for several seasons in vineyard blocks planted with three red-berried wine grape cultivars. Grapevines exhibiting GLD symptoms in these blocks were tested positive for Grapevine leafroll-associated virus 3 (GLRaV-3, genus: Ampelovirus, family Closteroviridae). The temporal spread of GLD indicated higher number of symptomatic vines in each season compared to previous seasons, suggesting increased incidence of the disease during successive seasons. The spatial distribution of symptomatic vines in all three blocks indicated a disease gradient in which the highest percentage of symptomatic vines were present in rows closest to old vineyard blocks showing GLD symptoms. Spatial autocorrelation (dependence) analysis indicated random distribution of symptomatic vines during initial years of post-planting suggesting primary spread and clustering of symptomatic vines during subsequent years suggesting secondary spread of GLD. Sequence analysis of a portion of the heat-shock protein 70 homolog gene encoded by GLRaV-3 revealed predominance of one of the several genetic variants of the virus in the three vineyard blocks. These results provided for the first time science-based knowledge on nature of the spread of GLD in young vineyards to pursue site-specific disease management strategies under conditions prevailing in Washington State.
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Details
- Title
- Molecular Biology and Epidemiology of Grapevine Leafroll-Associated Viruses
- Creators
- Bhanu Priya Donda
- Contributors
- Naidu A Rayapati (Advisor)Dennis A Johnson (Committee Member)Duroy A Navarre (Committee Member)George J Vandemark (Committee Member)Siddarame Gowda (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Plant Pathology, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 144
- Identifiers
- 99900581524101842
- Language
- English
- Resource Type
- Dissertation