Purification and properties of subterranean clover red leaf virus

Subterranean clover red leaf virus (SCRL V) was purified from infected peas using cellulase to assist in virus extraction. Yields of 0.5–3.0 mg/kg tissue were obtained. The virions were isometric with a diam. of 27 nm and sedimented as a single component of 114 S. The mean A260/A280 of purified preparations was 1.85. Apterae of Aulaeorthum solani (Kltb.) when fed on purified preparations through parafilm membranes were able to acquire and transmit virus. Purified virus had a dilution end point of 1.36 µg/ml, a thermal inactivation point between 55 and 60°C, and longevity in vitro of greater than 14 days. Gel electrophoresis of disrupted virions revealed that the coat protein was a single polypeptide with a molecular weight of 22 600. An antiserum with a homologous titre of 11256 in gel diffusion tests was prepared. SCRL V was shown to be serologically very closely related to soybean dwarf virus and less closely to bean leafroll, legume yellows, potato leaf roll, and tomato yellow top viruses. A more distant relationship was shown with beet western yellows virus. All the properties of SCRL V are consistent with it being a member of the luteovirus group and suggest that it is probably identical with soybean dwarf virus.