Purification and particle properties of groundnut rosette assistor virus and production of a specific antiserum*

Purified preparations of the luteovirus, groundnut rosette assistor virus (GRAV), were made by treatment of groundnut leaf extracts with cellulase, followed by sucrose density gradient centrifugation. Yields of virus particles were about 0·5-1·0 mg/kg leaf material. The preparations contained isometric particles c. 28 nm in diameter with a sedimentation coefficient (s_{20, w}) of 115 S, a buoyant density in Cs₂SO₄ of 1·34 g/cm³, and A₂₆₀/A₂₈₀ of 1·86. The particles contained a single species of nucleic acid (presumably RNA), of mol. wt 2·09 × 10⁶and with no detectable polyadenylate sequence, and a single protein species, of mol. wt 24 × 10³. An antiserum produced in a rabbit had a titre of 1/256 in gel diffusion tests and detected GRAV in leaf extracts by ELISA. GRAV particles reacted in F(ab')₂-ELISA and immunosorbent electron microscopy (ISEM) tests with antisera to bean leaf roll, potato leafroll and tobacco necrotic dwarf luteoviruses, but did not react with antisera to carrot red leaf luteovirus.