Heterogeneity of rice ragged stunt oryzavirus genome segment 9 and its segregation by insect vector transmission.

Genomic heterogeneity of genome segment 9 (S9) of rice ragged stunt virus (RRSV) was investigated and a point mutation was found to be responsible for an electrophoretic mobility shift of S9 on polyacrylamide gel electrophoresis (PAGE). A new form of S9 (S9L) which migrated slightly faster than natural S9 (S9U) had the same length with A-->C transversion at nt 843. Synthetic S9 with a C:G pair at nt 843 migrated slightly faster than that with an A:U pair. Therefore, we conclude that the single point mutation shifts the electrophoretic mobility. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), we could detect S9U and S9L alone or mixture in insect vectors after acquisition as well as in infected rice plants.