Genome composition analysis of multipartite BNYVV reveals the occurrence of genetic re-assortment in the isolates of Asia Minor and Thrace

Beet necrotic yellow vein virus (BNYVV) is the cause of rhizomania, an important disease of sugar beet around the world. The multipartite genome of the BNYVV contains four or five single-stranded RNA that has been used to characterize the virus. Understanding genome composition of the virus not only determines the degree of pathogenicity but also is required to development of resistant varieties of sugar beet. Resistance to rhizomania has been conferred to sugar beet varieties by conventional breeding methods or modern genome engineering tools. However, over time, viruses undergo genetic alterations and develop new variants to break crop resistance. Here, we report the occurrence of genetic reassortment and emergence of new variants of BNYVV among the isolates of Thrace and Asia Minor (modern-day Turkey). Our findings indicate that the isolates harbor European A-type RNA-2 and RNA-3, nevertheless, RNA-5 is closely related to East Asian J-type. Furthermore, RNA-1 and RNA-4 are either derived from A, B, and P-types or a mixture of them. The RNA-5 factor which enhance the pathogenicity, is rarely found in the isolates studied (20%). The creation of new variants of the virus emphasizes the necessity to develop new generation of resistant crops. We anticipate that these findings will be useful for future genetic characterization and evolutionary studies of BNYVV, as well as for developing sustainable strategies for the control of this destructive disease.