The detection of beet western yellows virus and beet mild yellowing virus in crop plants using the polymerase chain reaction.

Oligonucleotide primers were synthesised corresponding to conserved sequences between three isolates of beet western yellows virus (BWYV), flanking a 913 base fragment of BWYV genomic RNA. Using the polymerase chain reaction (PCR), these primers successfully amplified the target fragment in total RNA extracts from two oilseed rape plants infected with different isolates of BWYV. The PCR products were readily detected by staining with ethidium bromide following agarose gel electrophoresis, but the limit of detection could be increased further by Southern blotting. However, three isolates of beet mild yellowing virus (BMYV) in sugar beet did not give a signal which could be detected by ethidium bromide staining, although the target fragment could be detected by Southern blotting. The primers used have the potential to detect BWYV in crops with far greater sensitivity than enzyme-linked immunosorbent assay or nucleic acid hybridisation (dot-blotting) and may be capable of distinguishing between BWYV and BMYV. The application of PCR to detection and distinction of luteoviruses in general is discussed.