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Biological, Serological, and Molecular Variability Suggest Three Distinct Polerovirus Species Infecting Beet or Rape

First, sixth, and seventh authors: INRA, URVV, Vection et Lutte Intégrée, 28 rue de Herrlisheim, 68021 Colmar Cedex, France; second and fourth authors: IACR-Broom's Barn, Higham, Bury St. Edmunds, Suffolk, IP28 6 NP United Kingdom; third author: Université Lyon 1, Laboratoire d'Ecologie Microbienne, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France; and fifth author: IBMP (CNRS), 12 rue du Genéral Zimmer, 67084 Strasbourg Cedex, France

Yellowing diseases of sugar beet can be caused by a range of strains classified as Beet mild yellowing virus (BMYV) or Beet western yellows virus (BWYV), both belonging to the genus Polerovirus of the family Luteoviridae. Host range, genomic, and serological studies have shown that isolates of these viruses can be grouped into three distinct species. Within these species, the coat protein amino acid sequences are highly conserved (more than 90% homology), whereas the P0 sequences (open reading frame, ORF 0) are variable (about 30% homology). Based on these results, we propose a new classification of BMYV and BWYV into three distinct species. Two of these species are presented for the first time and are not yet recognized by the International Committee on Taxonomy of Viruses. The first species, BMYV, infects sugar beet and Capsella bursa-pastoris. The second species, Brassica yellowing virus, does not infect beet, but infects a large number of plants belonging to the genus Brassica within the family Brassicaceae. The third species, Beet chlorosis virus, infects beet and Chenopodium capitatum, but not Capsella bursa-pastoris.

Additional keywords: Beta vulgaris , Brassica napus , host specificity, luteovirus, monoclonal antibody, phylogenetic studies, taxonomy.