Purification and some properties of reovirus-like particles from leafhoppers and their possible involvement in wallaby ear disease of maize.

Reovirus-like particles, occurring in association with viroplasms, crystalline arrays and tubules, in the cytoplasm of Cicadulina bimaculata capable of inducing wallaby ear disease in maize, were purified from the insects by differential centrifugation, treatment with the nonionic detergent, Nonidet P-40, and sucrose density gradient centrifugation. The purified particles have a double-shelled icosahedral structure about 70 nm in diameter with external projections (A spikes) about 10 nm long located at the 12 vertices. These intact particles (IPs) are morphologically similar to those of Fiji disease virus (FDV), but are more stable. Cores were produced by enzymatic digestion of IPs with alpha-chymotrypsin. The cores are icosahedra about 57 nm in diameter with projections (B spikes) located at the 12 vertices, resembling those of FDV and cytoplasmic polyhedrosis virus. Immunization of a rabbit with purified IPs resulted in the production of antibodies specific to IPs, cores, and dsRNA. Immunoelectron microscopic investigations revealed that there is no relationship between this virus and FDV, maize rough dwarf, oat sterile dwarf, pangola stunt, and rice ragged stunt viruses, all members of the genus Fijivirus in the family Reoviridae. The nucleic acid extracted from partially purified virus was resolved into 10 segments by polyacrylamide gel electrophoresis. Reovirus-like particles or viroplasms could not be detected in thin sections of maize seedlings colonized by C. bimaculata showing wallaby ear symptoms. In the light of these data the possible etiology of wallaby ear disease is discussed.