Development of reliable detection assays for blueberry mosaic-and blackberry vein banding-associated viruses based on their population structures.

Blueberry mosaic associated virus (BlMaV), the presumed causal agent of the homonymous disease and blackberry vein banding associated virus (BVBaV), a component of the blackberry yellow vein disease complex, are recently characterized RNA viruses. There is a need for efficient and sensitive detection protocols for the two viruses, not only for screening during the nursery propagation process but also in commercial fields to better understand virus epidemiology and minimize disease spread. RNA viruses display significant nucleotide variation forming quasi-species. Therefore, sequence-based detection methodologies, even though sensitive, may lead to false negative results. For this reason, information on the genetic diversity of virus populations is essential to develop diagnostic assays that have the potential to detect all variants. Detection assays for BlMaV and BVBaV were developed based on existing genetic diversity data and were validated by screening samples from different geographical areas in the United States. These detection tests provide sensitivity and specificity and will serve as the protocols of choice for virus screening in Vaccinium and Rubus certification programs in the United States and elsewhere. Given the increasing global trade of both blueberry and blackberry these tests will be valuable in avoiding virus introductions to new areas.