Hydrangea mosaic virus, a new ilarvirus from Hydrangea macrophylla (Saxifragaceae).
This previously unrecognized virus was isolated from plants with chlorotic mosaic leaf symptoms in W. Sussex. It was mechanically transmitted without difficulty to 4 of 16 spp. from 3 of 5 families and was seed transmitted in Chenopodium quinoa, but not by aphids. Although relatively unstable in vitro, HydMV was purified by clarifying leaf extracts by emulsification with chloroform and acidification with citric acid, followed by differential centrifugation and sucrose density gradient centrifugation. Purified virus incompletely separated on sucrose density gradients into 3 components (T, M and B) with sedimentation coefficients (so20,w) of 86, 97 and 105 S respectively, but all particles had buoyant densities in CsCl of 1.37 g/cm3. The virus contained a single polypeptide species (mol. wt. 26.4 × 103), appeared quasiisometric to ovoid or elliptical, and measured c. 28 × 30 (T), 30 × 30 (M) or 30 × 32-38 nm (B). Single-stranded RNA species of mol. wt. 1.25, 1.08, 0.83, 0.36 and 0.27 (RNA-1 to 5 respectively) were obtained from virus preparations but mixtures containing RNA-1 to 3 plus either RNA-4 + 5 or the coat protein were infective. These properties suggest that HydMV has affinities with ilarviruses, though in tests it showed no serological relationship to any of 6 ilarviruses or 42 other viruses.