Detection and Molecular Variability of T urnip mosaic virus ( T u MV ) in S haanxi, C hina

Turnip mosaic virus ( T u MV ) is one of the most devastating threats to oilseed rape by causing serious crop losses. A total of 86 leaf samples of oilseed rape from eight different locations in S haanxi, C hina, were tested by RT ‐ PCR for T u MV ; the results revealed an infection level of 43% by T u MV . The complete coat protein ( CP ) gene of 32 T u MV isolates was cloned and sequenced. Analysis of the CP gene with sequences from the database allowed the genetic classification of 170 T u MV isolates or sequences. Four genetic clusters were obtained: MB (mostly B rassica isolates), MR (mostly R adish isolates), IBR (mostly I ntermediate between B rassica and R adish clusters) and OBR (mostly outside B rassica and R adish clusters). All subgroups were slightly related to the hosts, but unrelated to geographical origins. Most of S haanxi T u MV isolates were on separate branches, compared with the 138 known isolates originating from other parts of the world. Our results help provide a better understanding of the genetic diversity of T u MV isolates infecting oilseed rape in S haanxi, C hina.