Host range and molecular analysis of Beet leaf yellowing virus , Beet western yellows virus ‐ <scp>JP</scp> and Brassica yellows virus in Japan

Beet western yellows virus (BWYV; genus Polerovirus, family Luteoviridae) is one of the most important viruses causing yellowing disease of many field and vegetable crops. This study isolated different poleroviruses from sugar beet, spinach, radish and brassica in Japan, and identified them as BWYV‐JP, Beet leaf yellowing virus (BLYV), Brassica yellows virus (BrYV) and BrYV‐R (radish strain) based on host range and molecular analysis. Among over 100 plant species from 19 families inoculated with the vector Myzus persicae, about half of the species in 13 families were infected with some of these viruses. BLYV shared a similar host range to Beet mild yellowing virus (BMYV). These had a much more limited host range than BWYV‐JP, which resembled BWYV‐USA. The host range of BrYV was similar to that of Turnip yellows virus (TuYV). Phylogenetic analyses at the 5′ portion (replication‐related gene) of the genome showed that BLYV, BMYV, BWYV (‐JP and ‐USA) and Cucurbit aphid‐borne yellows virus (CABYV) formed one large group, whereas BrYV and TuYV were grouped together. BLYV and BWYV were most closely related to each other, and were more closely related to CABYV than to BMYV. However, at the 3′ end (coat protein gene), BLYV and BWYV‐JP formed a distinct group, separated from the BrYV group, which in turn was more closely related to BWYV‐USA, BMYV, TuYV and Beet chlorosis virus, a group originating from outside Asia. Thus, this study presents host range differences and phylogeographical relationships of BWYV‐like poleroviruses that are distributed worldwide.