Beet necrotic yellow vein virus and other soil-borne viruses in sugar beet

The worldwide extension of the rhizomania disease is one of the most worrying constraints that have to be faced by the sugar beet crop for the past 20 to 30 years.The disease is caused by the Beet necrotic yellow vein virus, a Benyvirus. The virus affects both the quantity and the quality of the production. But the major problem is probably lying in the long-term survival of the virus associated to its vector, Polymyxa betae, a soil-inhabiting plasmodiophoromycete. This vector has been also shown to transmit other viruses to sugar beet, like the Benyvirus, Beet soil-borne mosaic virus or the Pomovirus like the Beet soil-borne virus and the Beet virus Q. Control of rhizomania depends on the accurate and sensitive detection of BNYVV in plants and soil, for a precocious of infected fields and for breeding resistant sugar beet lines. Also, the complexity introduced by the co-occurrence with other soil-inhibating viruses raises needs for efficient detection techniques. Therefore, molecular diagnostic methods have been thoroughly used and developed for the identification and quantification of the Beet necrotic yellow vein virus as well as the other soil-borne sugar beet viruses and their vector. A description of sugar beet soil-borne viruses and their vector Polymyxa betae is therefore discussed in this chapter, focusing on the molecular diagnostic methods proposed for their detection and quantification, from serological to the polymerase-based methods