- Volume 59, Issue 2, 1982

The plaques formed by two calf rotavirus isolates differed in size and appearance. One isolate was more sensitive to homologous than to heterologous antiserum while the other was equally sensitive to both antisera.

After multiple sap transmissions two isolates of tomato spotted wilt virus (TSWV) lost the characteristic particles, and amorphous, more or less diffuse masses were observed in the cytoplasm of cells. The amorphous material, which had previously been described associated with normal virus particles, could also be found in pellets from extracts of infected plants. Isolates of the ‘amorphous’ type had the same thermal inactivation point as those of the normal ‘particulate’ type. It is suggested that the ‘amorphous’ type is a defective form of TSWV.