Genomic reassortment of rice dwarf Phytoreovirus (RDV) was experimentally demonstrated for the first time in plant reoviruses. Combinations of two genomic variants, most of the genomic segments of which could be distinguished by a high resolution polyacrylamide gel electrophoresis, were used to produce genomic reassortants. After artificial mixed injection of two of three isolates (RDV-S, RDV-AI, and RDV-AN) into the insect vector Nephotettix cincticeps, rice seedlings were sequentially inoculated and the genomic origin of the viruses present in the infected plants was examined by electrophoresis. The progeny virus population contained either one or both of the respective genomic segments from the parents. Genomic segments reassorted randomly except for genome segment 1 (S1) and S9. S9 of RDV-S was mostly excluded in the reassortants in both the insects and the infected plants when it was mixed with RDV-AI or RDV-AN. On the other hand, S9 reassorted randomly in most of the virus populations in infected plants when RDV-AI and RDV-AN were co-injected into insects. When RDV-S and RDV-AI were mixed, S1 from RDV-S was present more frequently in the infected plants although both parental S1's were present in equimolar amounts in insects.