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 vi rus (RRSV) was investigated and a point mutation was found to be respo nsible for an electrophoretic mobility shift of S9 on polyacrylamide g el electrophoresis (PAGE). A new form of S9 (S9L) which migrated sligh tly faster than natural S9 (S9U) had the same length with A --> C tran sversion at nt 843. Synthetic S9 with a C:G pair at nt 843 migrated sl ightly faster than that with an A:U pair. Therefore, we conclude that the single point mutation shifts the electrophoretic mobility. Using p olymerase 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.