The occurrence of rice black-streaked dwarf Fijivirus (RBSDV) was recorded in Hokkaido for the first time. In 1992, rice plants with symptoms similar to those of RBSDV were observed in Asahikawa, Hokkaido. One field isolate (AC) of the disease agent was transmitted to rice, barley, wheat and maize by the planthopper, Laodelphax striatellus. In enzyme-linked immunosorbent assay using antibodies to RBSDV, the AC isolate was serologically related to RBSDV. A partially purified preparation from a rice plant infected with the AC isolate revealed spherical virus particles of about 60 nm in diameter with spikes typical of RBSDV. When ds RNAs were extracted from the rice plant infected with the AC isolate and analyzed in Laemmli's 10% polyacrylamide gel electrophoresis, the AC isolate contained 10 segmented ds RNAs. Co-electrophoresis of ds RNAs from RBSDV maintained at Hokkaido University (RBSDV-H), and from the AC isolate showed a very similar but distinct electrophoretic pattern. In RNA-RNA hybridization, all the genomic segments of the AC isolate reacted with total genomic RNAs of RBSDV-H labelled at their 5' termini. Furthermore, three field isolates (AC, AG, AS) reacted with RBSDV specific probe in dot blot hybridization intensely. Based on these results, the AC isolate was identified as RBSDV. In 1993, rice fields were surveyed for the occurrence of RBSDV, RBSDV was isolated from rice plants collected in several locations vicinities of Asahikawa.
