Submitted to: International Plant Virus Epidemiology Symposium
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2010
Publication Date: June 20, 2010
Citation: Stenger, D.C. 2010. Sequence polymorphism of a glassy-winged sharpshooter phytoreovirus reveals a bottleneck in the Californian population. International Plant Virus Epidemiology Symposium Scientific Program. P.82. Technical Abstract: The glassy-winged sharpshooter (GWSS; Homalodisca vitripennis Germar) is an invasive insect introduced to California circa 1989. Native to the southeastern U.S. and northeastern Mexico, GWSS is of economic concern as a vector of the Pierce’s disease bacterium Xylella fastidiosa. Recently, a novel phytoreovirus species (Homalodisca vitripennis reovirus, HoVRV) infecting GWSS was characterized. As viral genomes evolve at a rate many log units greater than their hosts, it was postulated that HoVRV polymorphism may serve as a marker to discriminate GWSS populations. Complete genome sequences of five Californian and four southeastern HoVRV isolates were evaluated for polymorphism. Pairwise diversity was ~10-fold less for HoVRV in California (~0.1%) compared to the southeastern U.S. (~1%). Phylogenetic analysis of each dsRNA segment indicated that the Californian isolates grouped as a monophyletic lineage. In contrast, relative placement of southeastern U.S. isolates varied among dsRNA segments. To sample diversity at single locations, dsRNA Segment 11 was sequenced for nine additional isolates each from Riverside, CA and Johnston Co., NC. Whereas 9 of 10 Riverside isolates were identical (the tenth varied at one position), diversity among Johnston Co. isolates approached that of the southeastern U.S. population. Coalescent analyses estimated median age of the Californian population at 11.6 to 26.3 years, depending upon the demographic model employed. Estimates of median clock rate for the Californian population were 1.662 X 10-5 to 5.502 X 10-5 nt substitutions/site/year. Collectively, the results indicate that HoVRV diversity in the native range of GWSS was high relative to a newly established population, and that the Californian population of HoVRV was subjected to a bottleneck coinciding with introduction of GWSS. By proxy, the results suggest that GWSS establishment in California resulted from a limited introduction and that HoVRV genotype may serve to identify source of the Californian GWSS population.