Evaluation of Soybean Vein Necrosis-Associated Virus Infected Soybean for Seed Transmission

A new soybean virus, Soybean Vein Necrosis-associated Virus (SVNaV), was widespread in KY and much of the Midwest d uring 2012. Very little is known about this emerging virus disease, including possible yield/quality impacts, disease spread and development, variation in virus, variation in soybean response to infection, control, and interactions with other pests. At the present time, scientists do not have the ability to inoculate plants with consistency and at will; however, the virus can now be positively indentified using an anti-serum/antigen-based diagnostic protocol (ELISA), so detailed work on the virus in now possible. The virus has been shown to be transmitted by thrips, but it is unknown whether these insects are the primary means by which SVNaV spreads in soybean. Seed transmission of SVNaV has not been studied, but could be an important means of virus transmission and long distance spread. Observations suggest that soybean cultivars differ in susceptibility to SVNaV, or at least vary in the degree of symptom expression. But resistance genes have yet to be identified and no SVNaV-resistant cultivars are available. SVNaV is now widespread in occurrence in the U.S., but has not been detected outside the U.S. Thus, concerns and regulation of seed and grain exports from the U.S. could arise in the near future. If the virus is proven not to be transmitted by seed, then the likelihood that burdensome export restrictions would be devised would be greatly minimized. Farmers and seed dealers would also be relieved knowing that SVNaV is not seed transmitted. Conversely, if it turns out that SVNaV is seed transmitted, that is essential information for developing control strategies for the disease. Preliminary data suggest that SVNaV is limited in genetic variation. However, more detailed studies must be conducted, using virus populations collected from different soybean cultivars and locations. If divergent populations are found to exist, this might facilitate efforts to identify and breed resistant cultivars, as well as facilitate the development of more specific virus diagnostic protocols. We propose to study SVNaV in non-harvest rows of the 2013 UK Soybean Variety Test, which will be planted at the UKREC in Princeton, KY. Thus, at the end of our experiments, we will have studied variation in both host and virus. Studies will allow us to answer the question of possible or lack of seed transmissibility regardless of soybean or virus genotypes conclusively.