Date Published: August 1, 2013
Publisher: Public Library of Science
Author(s): Robin MacDiarmid, Brendan Rodoni, Ulrich Melcher, Francisco Ochoa-Corona, Marilyn Roossinck, Glenn F. Rall.
Human activity is causing new encounters between viruses and plants. Anthropogenic interventions include changing land use, decreasing biodiversity, trade, the introduction of new plant and vector species to native landscapes, and changing atmospheric and climatic conditions. The discovery of thousands of new viruses, especially those associated with healthy-appearing native plants, is shifting the paradigm for their role within the ecosystem from foe to friend. The cost of new plant virus incursions can be high and result in the loss of trade and/or production for short or extended periods. We present and justify three recommendations for plant biosecurity to improve communication about plant viruses, assist with the identification of viruses and their impacts, and protect the high economic, social, environmental, and cultural value of our respective nations’ unique flora: 1) As part of the burden of proof, countries and jurisdictions should identify what pests already exist in, and which pests pose a risk to, their native flora; 2) Plant virus sequences not associated with a recognized virus infection are designated as “uncultured virus” and tentatively named using the host plant species of greatest known prevalence, the word “virus,” a general location identifier, and a serial number; and 3) Invest in basic research to determine the ecology of known and new viruses with existing and potential new plant hosts and vectors and develop host-virus pathogenicity prediction tools. These recommendations have implications for researchers, risk analysts, biosecurity authorities, and policy makers at both a national and an international level.
Over the last 60 years, global trade has changed significantly with the formation of the World Trade Organization (WTO) in 1995  and the establishment of multiple trade agreements between countries and jurisdictions all aiming at reducing obstacles to international trade. Agreements such as the Sanitary and Phytosanitary (SPS) Agreement have promoted trade liberalization and harmonization of biosecurity measures and agri-food standards but have also facilitated the intracontinental and intercontinental movement of insects and pathogenic microbes that disturb native and exotic ecosystems –. The frequency of incursions of unwanted organisms into these globalized pathways is increasing and leads to emergence of diseases and pests that are costly to control and/or eradicate –.
As the knowledge of virus identity is extended, an equal, if not increased, effort is required to discover viruses’ roles in their existing and potential new ecosystems. In particular, since many newly discovered viruses will be derived from infections of native plant hosts, it is vitally important for biosecurity agencies to survey for the presence of plant viruses in their own native flora.
The distinction between a virus as a physical entity and an in-silico virus species that encompasses actual viruses is important when considering naming of viruses , . The provision in publications of the italicized name of a virus species indicates that the virus is a true member of a recognized virus species. Conversely, a non-italicized name is usually an invention of the authors of the original publication about the virus and is listed as a tentative virus species by the International Committee for the Taxonomy of Viruses (ICTV).
An initial biosecurity investigation might escalate to a full investigation or incursion response when a new or regulated virus, not yet established, is detected within the country’s environment. Risk assessment and analysis are the first steps in assessing the economic, social, environmental, or cultural impacts of the new incursion. If the impacts are high, quarantine agencies will assess the various options available. If the likely impacts are low, normally, no further official action is taken. It is therefore important to understand the existing and potential plant virome in our ecosystems. Viruses are part of the wider ecosystem and some interactions may result in disease while other interactions may be beneficial to the host plant.
The intercontinental mobilization of the human population has assisted the spread of infectious diseases on a global scale. This was clearly demonstrated for over half the Australian potyvirus species that have been introduced during the last two centuries by European migrants . Plant virus incursions occur regularly and most are recorded on international databases (e.g., http://www.promedmail.org). These incursions often result in trade restrictions and the introduction of strict phytosanitary measures on the local industry to prevent further spread and/or to eradicate the pest.