Recombination in plant RNA viruses

Owing to increased global travel of humans carrying plants and viral vectors, introduction of new agricultural practices in combination with climate changes, the emergence of new viruses and novel viral variants is a major, continuing threat to human health and welfare. RNA recombination is one of the major forces in increasing plant virus variability and adaptation to new hosts, often leading to emergence of new variants and resistance-breaking virus strains. RNA recombination can also increase the fitness of plant RNA viruses by repairing defective viral genomes or efficiently removing deleterious mutations that result from error-prone replication. The frequency of RNA recombination is affected by several factors, including the viral replication proteins and various features of the viral RNA templates involved. Host genes also affect viral RNA recombination, suggesting complex interaction between a given virus and its host during viral adaptation and evolution. This chapter summarizes our current knowledge on this evolutionarily important process and its roles in emergence of new viruses or viral variants with altered pathogenecity.