Evolutionary genetics factors underlying the emergence and spread of plant RNA viruses
S. F. ELENA (1). (1) IBMCP-CSIC, Valencia, Spain
An emerging virus is the causative agent of an infectious disease whose incidence is increasing following its first appearance in a new host population as a result of long-term epidemiological changes. The sources of emerging viruses are reservoir species in which the pathogen is already well established. Over recent years, agriculture has been seriously compromised by a succession of epidemics caused by new viruses that switched host species (e.g. <i>Tomato torrado virus</i>), or new variants of classic viruses that acquired virulence factors (e.g. necrogenic <i>Cucumber mosaic virus</i>). Although viral emergence has been associated with ecological change or agronomical practices bringing in contact reservoirs and crop species, the picture is much more complex and results from an evolutionary process in which the main players are the changes in ecological factors, virus’ genetic plasticity, host factors required for virus replication (including active defence mechanisms), and a strong stochastic component. I will review relevant evolutionary genetics concepts useful to understand emergence (e.g. mutation and recombination rates, <i>G</i>x<i>E</i> interactions and epistasis on mutational effects, metapopulation dynamics). I will also discuss whether emergence requires adaptation to the new host at early stages of infection or it is a stochastic process involving transmission of a pre-existing strains. Finally, I will discuss why certain types of viruses are more prone to emerge than others.
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