A Dwarf Disease on Rice，Wheat and Maize from Zhejiang and Hebei is Caused by Rice Black-streaked Dwarf Virus

Two isolates of plant reoviruses causing severe stunting and dark leaf symptoms on wheat and maize from Hebei province and on rice from Zhejiang province have been characterized.The virus particles of both isolates were about 60～80nm in diameter and closely related serologically.Their dsRNA electrophoretic profiles in agarose gel were similar.They were both transmitted efficiently by the planthopper Laodelphax striatellus to maize and rice from their original hosts but maize was not a very suitable host for the vector and was a poor source of virus.Two fragments corresponding to dsRNA parts of rice black-streaked dwarf virus(RBSDV)S7 and S8 were amplified by RT-PCR from both isolates and sequenced.There were 97.0～98.9% identical nucleotides between the two Chinese isolates,which appear to be RBSDV(92.2%～95.5% identical nucleotides to Japanese isolate)rather than maize rough dwarf virus(79.6%～88.4% identical nucleotides to Italian isolate).