Occurrence in the United Kingdom of <i>Beet necrotic yellow vein virus</i> isolates which contain RNA 5

Abstract

Rhizomania, a very damaging disease of sugar beet (Beta vulgaris), is caused by Beet necrotic yellow vein virus (BNYVV) (Tamada & Baba, 1973). BNYVV isolates can be divided into different pathotypes, one of which includes isolates that contain an additional genomic RNA (RNA 5) (Tamada et al., 1989). BNYVV isolates containing RNA 5 have been reported previously from Europe (near Pithiviers, France), Japan, China and Kazakhstan (Koenig & Lennefors, 2000). There is some evidence to suggest that isolates containing RNA 5 are more pathogenic than those of the other pathotypes (Tamada et al., 1996). It was decided therefore to determine whether such isolates occurred in the UK, where BNYVV has been present since 1987. Since 2000, as part of the annual rhizomania survey covering England and Wales, all samples confirmed as BNYVV-positive by ELISA were also tested for RNA 5 using an RT-PCR assay. In 2001, two isolates (designated CSL 2001-64 and 2001-115) from an area of Norfolk, west of Norwich, were shown to be PCR-positive. These results were confirmed by using both a specific TaqMan® RT-PCR assay and conventional RT-PCR using a different pair of RNA 5-specific primers which gave a single product of the correct predicted size (530 bp). These products were then sequenced (Accession Number AJ439620) and were found to be identical. Database searches revealed that the partial sequence of the two UK isolates had 94–100% identity with that of 29 different published BNYVV RNA 5 sequences. The sequence of the UK isolates had the closest homology with two BNYVV P pathotype isolates from France (accession numbers ABO18618-9). This is the first record of BNYVV isolates containing RNA 5 occurring in UK sugar beet crops. This work was funded by the UK Department of the Environment, Food and Rural Affairs and was carried out under licence numbers PHL 100/2637(2000), PHL 251/100 A/3719(02/2001) Amended (10/2001), PHL 251/4070 (01/2002).