Viruses and Reciprocal Influences Between Natural Ecosystems and Agroecosystems

Once understood to be influential largely in agroecosystems, plant viruses are now seen as integral parts of natural ecosystems worldwide. As a result, movement of viruses between natural and managed ecosystems can exert reciprocal effects on both. Historical agricultural experience has demonstrated, for example, that crops introduced to new environments can be at risk for infection from viral reservoirs in wild plants. More recent studies in natural communities indicate that virus pressure on wild plants may likewise be altered by interactions with agricultural and weedy plant species and that this pressure can have substantial ecosystem consequences, even contributing to large-scale land cover change. One path of reciprocal influence among agricultural and natural plant communities results from the synergy achieved when viruses and vectors gain access to different plant types that provide separate but critical resources. For example, when fast-growing susceptible crops or weeds that amplify vector and virus populations come into close proximity with perennial hosts that serve as long-term reservoirs, there is strong potential for an overall increase in virus pressure that can influence agricultural and natural communities alike. These issues of virus amplification and persistence deserve special consideration in future bioenergy landscapes, where wide-scale manipulation and planting of new perennial crops is foreseen. Modification of long-lived perennial species for fast growth in high-production systems has potential to unite into one crop type the critical characteristics of both virus amplifier and reservoir. Strategies to avoid virus proliferation require consideration both of plant traits and landscape characteristics that promote pest suppression.