Environment and evolution modulate plant virus pathogenesis.

The study of plant viruses has focussed on those causing diseases in crops and, only recently, in wild plants. However, increasing evidence shows that plant viruses often are neutral, or even beneficial, for their hosts. Thus, plant viruses can be conditional mutualists, although the underlying mechanisms have been seldom analyzed. Little is known about what environmental factors modulate virus pathogenesis, and how. A major factor can be higher horizontal transmission rates in agricultural than in wild ecosystems. However, ecosystem simplification in human-managed habitats may result in changed epidemiological factors that influence pathogenesis. The interplay between ecology, evolution and pathogenesis awaits further research.