Comparison of Particle Properties of Heracleum Latent and Apple Chlorotic Leaf Spot Viruses

Purified preparations of heracleum latent virus (HLV), which has very flexuous filamentous particles of about 730 x 12 nm, contain a single sedimenting component with s⁰_20,w = 96 S, A₂₆₀/A₂₈₀ = 1.50 and buoyant density in Cs₂SO₄ = 1.24 g/ml. The particles possess a single polypeptide, mol. wt. 23500, apparently lacking in tryptophan, and a single-stranded RNA of apparent mol. wt. 2.3 x 10⁶ in nondenaturing conditions or 2.15 x 10⁶ in denaturing conditions. The infectivity of the particles is sensitive to ribonuclease; this sensitivity is increased after exposure to EDTA, but is not decreased by addition of Mg²⁺ or Ca²⁺. HLV thus closely resembles apple chlorotic leaf spot virus, to which it is serologically unrelated; it is regarded as a tentative member of the closterovirus group. Its cryptogram is R/1:2.3/(5):E/E:S/Ve/Ap.

^* Present address: Benaki Phytopathological Institute, Kiphissia, Athens, Greece.