PROPERTIES OF A FILAMENTOUS VIRUS ISOLATED FROM GRAPEVINES AFFECTED BY CORKY BARK

A virus with highly flexuous filamentous particles c. 800 nm long, sho wing 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 ra nge and was experimentally transmitted by the mealybug Pseudococcus fi cus. The physicochemical and ultrastructural properties of GVB resembl e those of closteroviruses. However, it is serologically unrelated to other grapevine closteroviruses including grapevine virus A, with whic h it shares some biological and physicochemical properties.