Some properties of a hitherto undescribed filamentous virus of the grapevine

An apparently new, non mechanically-transmissible clostero-like virus, for which the name ''grapevine leafroll-associated virus 7('') (GLRaV-7) is proposed, was found in Albanian grapevine accessions. Virus particles were filamentous, had conspicuous cross banding and a length of 1500-1700 nm. Virions had coat protein subunits with an estimated M(r) of ca. 37 kDa and a ssRNA genome with size of ca. 19.5 kb as deduced from the estimate of dsRNA (ca. 19.5 kbp) extracted from grapevine tissues. A virus-specific antiserum was raised, which decorated virions at a dilution of 1:1000. This antiserum did not recognize particles of any of the six grapevine leafroll-associated clostero-like viruses (GLRaV-1 to -6) known to date, nor of grapevine trichovirus A (GVA) and B (GVB). Grapevine indicators graft-inoculated with material from accessions containing GLRaV-7 reacted with mild leafroll-like symptoms. In a survey in which 2226 vines from 30 different countries were examined by ELISA, GLRaV-7 was found in 141 plants from Albania, Greece, Hungary, Egypt, and Italy.