Rhizomania is a major soil-borne disease of sugar beet. There is a major concern about the emergence of resistance-breaking isolates of the virus in intensive beet cropping areas, though up to now several hypothesis are still under investigation to explain the phenomenon. With the view of unraveling the question, extensive surveys were conducted in severely disease-affected areas in Europe around the Pithiviers area (France), in Belgium as well as in Asia in countries like Turkey or Iran. Root samples collected from both in disease-affected or non disease-affected areas were tested for the presence of Beet necrotic yellow vein virus, causal agent of the disease or of other soil-borne viruses like Beet soil-borne virus, Beet virus Q and Beet black scorch virus. Samples were tested by RT-PCR for the detection of BNYVV. A specific fragment was amplified from the gene P25 located on RNA-3 and from the gene P26 located on RNA-5. Results from the analysis of more than 400 samples reveal a wide range of variations within the BNYVV RNA-3 as well as contrasting situations according to the area surveyed, with evidences for mix BNYVV type infections. Methodological questions regarding the virus distribution in the root, presence and distribution of the virus in the soil will be addressed.

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