Size of dsRNA Genome Segments of Rice Dwarf and Rice Ragged Stunt Viruses Determined by Electron Microscopy

Molecular weights of genome RNA segments of rice dwarf virus (RDV) and rice ragged stunt virus (RRSV) were estimated by electron microscopy. The segments separated by polyacrylamide gel electrophoresis were examined using a cytochrome C metho. Estimated molecular weights of the RDV segments 1 to 12 were 2.92, 2.27, 2.18, 1.69, 1.60, 1.07, 0.97, 0.93, 0.82, 0.85, 0.59 and 0.55×10 6 , respectively. These values were in good agreement with those estimated by polyacrylamide gel electrophoresis under denaturing condition (Uyeda and Shikata, 1984). However, in the case of the segments 8 to 12, the values were higher than those determined by electrophoresis under non-denaturing condition using reovirus (type 2 or 3) or cytoplasmic polyhedrosis virus of Bombyx mori as a size marker. Genome size of RRSV was also reestimated and the segments 6 to 10 were found to be larger than those previously determinde. Reliability of sizing of dsRNA by electron microscopy is discussed