Properties of a filamentous virus isolated from grapevines affected by corky bark

A virus with highly flexuous filamentous particles c. 800 nm long, showing distinct transverse striations was isolated with high frequency (60%) by inoculation of Nicotiana occidentalis with sap from grapevine accessions indexing positive for corky bark. The virus, for which the name grapevine virus B (GVB) is proposed, has an ssRNA genome with mol. wt. of c. 2.5 x 10(6) Da (c. 7600 nt) and coat protein subunits with mol. wt. of c 23,000 Da. GVB has a very restricted herbaceous host range and was experimentally transmitted by the mealybug Pseudococcus ficus. The physicochemical and ultrastructural properties of GVB resemble those of closteroviruses. However, it is serologically unrelated to other grapevine closteroviruses including grapevine virus A, with which it shares some biological and physicochemical properties.