DETECTION OF BMYV AND BWYV ISOLATES USING MONOCLONAL-ANTIBODIES AND RADIOACTIVE RNA PROBES, AND RELATIONSHIPS AMONG LUTEOVIRUSES

In order to discriminate between sugar beet infecting beet mild yellowing virus (BMYV) and other isolates of beet western yellows virus (BWYV), monoclonal antibodies (MAbs) and radioactive riboprobes were used. With MAbs prepared against BMYV or potato leafroll virus (PLRV) no distinction could be established between BMYV and BWYV. Seven probes were synthesised from a lettuce infecting BWYV isolate; their localisation in the genome is known and they cover almost its entire length. Probes from the 3' part of the genome hybridised with all BMYV and BWYV isolates whereas those from the 5' part did not recognise BMYV isolates, showing that a divergent 5' region exists in the genomes of BMYV and BWYV. Probes also readily detected the virus in single aphids. The relevance of this finding for epidemiological studies is discussed. MAbs and riboprobes were also tested against other luteoviruses (PLRV; barley yellow dwarf virus (BYDV) MAV, PAV and RPV strains). The serological relationship between BMYV and PLRV was confirmed and an epitope common to PLRV and BYDV-RPV was found. Using probes, PLRV and BYDV-RPV were found to share domains of homology with BWYV. BYDV-PAV showed weak homology with BWYV, while BYDV-MAV showed none.