Temporal and Spatial analyses of Dasheen mosaic virus
Chang, Wee Leong
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Exploring the genetic diversity and evolutionary history of plant viruses is critical to understanding their ecology and epidemiology. Like many other plant RNA viruses, Dasheen mosaic virus (DsMV) is an important and conspicuous viral disease of ornamental and edible aroids throughout the South Pacific and worldwide, but its population diversity and variability are poorly understood. To further investigate this virus, phylogenetic and population genetics based methods were used to investigate the temporal and spatial dynamics of the evolutionary mechanism and genetic variability among the DsMV isolates. A selected region of the coat protein (CP) gene was amplified and sequenced to infer genetic relationships between viral isolates at the temporal and spatial scales. This study demonstrated that genetic variation occurs between the DsMV isolates. The population structure of DsMV consisted of the consensus sequence and a pool of mutants that are not identical but are closely related to the consensus sequence, and it coincides with the quasispecies concept described for many RNA viruses. The quasispecies-like nature of the DsMV population suggested that the virus is capable of rapid evolution and adaptation in response to changing ecological factors and agricultural practices. Analysis of DsMV isolates on a temporal scale suggested the role of stochastic or selection-fitness levels are the key mechanisms in the dynamics of plant virus population genetics and evolution. In contrast, spatial analysis suggested that diversification and spread of DsMV have been concomitant with an extension of human migration and taro/tannia cultivation in the South Pacific islands. The combined actions of genetic drift and selection pressure have continually remoulded this diversity. Thereby, creating a geographic mosaic in the degrees of diversity found within and between geographic regions.