Comparison of the beet necrotic yellow vein virus P75 nucleotide sequences of Belgian type A and type B sources.

RNA-2 P75 open reading frame sequencing was conducted on BNYVV-infected sugar beet plants originating from 10 Belgian sources and was compared with sequences originating from France, Kazakhstan, Japan and China. This allowed the characterization of types A and B in Belgium. Sequence analysis confirmed that type A is intermediate between types P and B. The analysis of nucleotide sequences of the capsid protein epitopes and of different motifs involved in the transmission of the virus to the plant by Polymyxa betae reveals that they are well conserved among the different sequences analysed. In silico analysis showed that a potential dimerization/dsRNA-binding domain is present on P75. Finally, in order to compare the different BNYVV types, a real-time quantitative (RT)-PCR targeting the readthrough domain of P75 was developed and assessed over a period of 40 days on BNYVV susceptible sugar beet cv. Cadyx.