Purification and characterization of rice tungro virus by analytical density-gradient centrifugation

Abstract

The leafhopper-borne rice tungro virus (RTV) was purified by heating leaf extracts in 0.01 M EDTA, pH 7–8, at 40° for 1 hour followed by differential centrifugation and by rate zonal centrifugation in sucrose density-gradients. Some of its physicochemical characteristics were determined by analytical density-gradient centrifugation. The virus withstood temperatures below 63° for 10 minutes, pH up to 9, without apparent denaturation and did not denature in vitro for more than 24 hours at room temperature. The virus concentration in the plant was low. The particle was a polyhedron of 30–33 mμ diameter with a sedimentation coefficient of 175 ± 5 S. Infectivity was associated with the zone in the sucrose density-gradient columns containing these particles. The feasibility is emphasized of determining physicochemical characteristics by analytical density-gradient centrifugation for viruses difficult to transmit mechanically.