RELATIONSHIPS AMONG TRIALEURODES-VAPORARIORUM - TRANSMITTED YELLOWING VIRUSES FOR EUROPE AND NORTH-AMERICA

Beet pseudo-yellows virus (BPYV), a possible closterovirus first identified in California, has long been thought to cause economically important whitefly-transmitted diseases worldwide, although serological and molecular evidence for this is lacking. A yellowing virus prevalent in the UK in 1988, originally thought to be identical to BPYV, was shown by a specific reverse transcription polymerase chain reaction (RT-PCR) test to differ from BPYV and from other whitefly-transmitted yellowing viruses from France, The Netherlands; Spain and Turkey. Sequence analysis of a putative polymerase gene of the virus showed that it differed from known closterovirus genes, results suggesting that the virus may be an uncharacterized species. Following development of an RT-PCR test diagnostic for currently prevalent whitefly-transmitted yellowing viruses, a second virus was shown to be different from that found in 1988 but closely related to BPYV and the other yellowing viruses from Europe. This is the first direct evidence of a relationship between the latter and BPYV.