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Rice infectious gall virus
Rice ragged stunt virus is a plant pathogenic virus of the family Reoviridae.
RRSV, vectored by the brown planthopper , causes ragged stunt disease of rice. The virus, first described by Hibino, Ling and Shikata, is also less commonly known as rice infectious gall virus. RRSV has polyhedral particles about 50 nm in diameter possessing spikes to a diameter of 65 nm. The particles contain double-stranded RNA in eight segments. RRSV can only infect plants in the family Gramineae, i.e. grasses including rice. The virus can only be transmitted by BPH and is not mechanically transmitted to plants.
Rice plants infected with RRSV are stunted with whitish spindle-shaped outgrowths. Later the infected leaves become twisted with ragged edges, and may eventually turn brown. Rice plants may survive the infection, but yields are greatly reduced due to delayed flowering, incomplete panicle emergence, and unfilled grains. Symptoms of RRSV infection vary with the variety of rice and stage of growth. Most rice varieties of Oryza sativa japonica and Oryza sativa indica are susceptible to RRSV though several resistant varieties are available. Attempts to prevent RRSV infections by controlling BPH with insecticides often have the opposite effect of facilitating RRSV outbreaks; this can be due to a disproportionate effect of insecticides on the natural enemies of BPH. Certain types of insecticides increase the birthrates of BPH through their effects on the reproductive systems of male and female planthoppers. The increase in BPH populations not only increases the incidence of RRSV within a field, but as the BPH become crowded they transform into long-winged migratory forms and spread RRSV to fields up to hundreds of kilometers away.