Detection of double-stranded RNA by serologically specific electron microscopy

Details of a procedure for detecting double-stranded RNA (dsRNA) in virus and viroid infected tissue extracts using serologically specific electron microscopy are given. A method for staining dsRNA, based on in situ formation of uranyl phosphate, that consistently permits the examination of dsRNA by electron microscopy without shadowing with heavy metals, is described. The method provides for routine assays for dsRNA in crude extracts without the variable results associated with shadowing procedures. DsRNA was found to accumulate in older leaves of sorghum systemically infected with sugarcane mosaic virus. In contrast, dsRNA was not detected in older cowpea leaves systemically infected with cowpea mosaic virus but was readily found in inoculated leaves 4 days post inoculation and young systemically infected leaves.