Evolutionary Constraints on Emergence of Plant RNA Viruses
Santiago F. Elena
from: Recent Advances in Plant Virology (Edited by: Carole Caranta, Miguel A. Aranda, Mark Tepfer and J.J. Lopez-Moya). Caister Academic Press, U.K. (2011)
Over the recent years, agricultural activity in many regions has been compromised by a succession of devastating epidemics caused by new viruses that switched host species, or by new variants of classic viruses that acquired new virulence factors or changed their epidemiological patterns. Although viral emergence has been classically associated with ecological change or with agronomical practices that brought in contact reservoirs and crop species, it has become obvious that the picture is much more complex, and results from an evolutionary process in which the main players are the changes in ecological factors, the tremendous genetic plasticity of viruses, the several host factors required for virus replication, and a strong stochastic component. The present chapter puts emergence of RNA viruses into the framework of evolutionary genetics and reviews the basic notions necessary to understand emergence, stressing that viral emergence begins with a stochastic process that involves the transmission of a pre-existing viral strain with the right genetic background into a new host species, followed by adaptation to the new host during the early stages of infection read more ...