Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 14, 2010
Publication Date: July 1, 2010
Citation: French, R.C. 2010. Population Processes and Plant Virus Evolution. Abstract presented at American Phytopathological Society Annual Meeting. Phytopathology Volume 100:S149. Technical Abstract: The number of studies detailing levels of sequence diversity within plant virus populations are growing at a rapid pace. At the same time, recent work has provided empirical estimates of parameters important in the life cycle of plant viruses, which in turn can help in understanding observed patterns of polymorphism. Despite the fact that plant viruses are prolific replicators, producing upwards of millions of virions per cell, they are subjected to severe genetic bottlenecks at virtually all stages of growth, including cell to cell movement, systemic infection, and horizontal transmission to new hosts. Thus, the effective population size (Ne) of plant viruses is many orders of magnitude smaller than their census numbers. Ne is of crucial importance in determining both the rate of genetic drift in a population (drift is faster in smaller populations), and the efficacy of selection relative to drift. Evidence also suggests that intracellular replication of RNA viruses (as well as DNA viruses replicating by a rolling circle mechanism) is a nearly linear ‘stamping machine’ process. This profoundly reduces the number of mutant genomes that are produced in a viral population. A ‘stamping machine’ mode of replication also increases the variation in offspring number among potential parental genomes and reduces Ne. Nevertheless, strong selection can still effect changes even in small populations, with better adapted genotypes replacing those with deleterious mutations.