Characterization of broccoli necrotic yellows virus

Abstract

Broccoli necrotic yellows virus (BNYV) had a limited host range by sap inoculation—3 of 17 plant species were infected including Datura stramonium from which it was characterized. The virus was not seed-borne, its longevity in vitro was between 1 and 3 days at 4 ° and less than 1 day at 23 °, its dilution end point was between 10 −3 and 10 −4, its thermal inactivation point between 45 ° and 50 °. BNYV was sensitive to ether indicating it contains lipid. The virus was purified by a combination of Celite filtration, differential centrifugation, chromatography on a hydroxyapatite column and density-gradient centrifugation in either sucrose or potassium tartrate. Partially purified BNYV (before density-gradient centrifugation) had S 20, ω = 874 S ± 41S and a buoyant density of 1.183 g/ml whereas purified BNYV (after density-gradient centrifugation) had S 20, ω = 751 ± 75 and a buoyant density of 1.195 g/ml. BNYV contains RNA. A specific antiserum to BNYV reacted to form one to three precipitation lines with concentrated or purified BNYV. Purified preparations stained in 2% potassium phosphotungstate contained bullet-shaped particles with a mean size of 266 × 66 nm and occasional bacilliform particles. In later trials with uranyl acetate, BNYV was bacilliform (275 ×75 nm). The bullet shape of particles stained in KPT is an artifact produced by the stain.