FIG LATENT VIRUS 1, A NEW MEMBER OF THE FAMILY FLEXIVIRIDAE

A virus with filamentous particles ca. 700 nm long, denoted Fig latent virus 1 (FLV-1) is widespread in Apulian (southern Italy) fig orchards, in trees showing or not mosaic symptoms and in symptomless seedlings. FLV-1 was transmitted mechanically to a restricted range of herbaceous hosts without inducing apparent symptoms, through seeds at a very high rate, and was purified from root tissues of infected figs. A virus-specific antiserum proved useful for FLV-1 detection in fig leaf dips by immunosorbent electron microscopy. Bundles of filamentous particles were observed in the cytoplasm of parenchyma cells of infected fig trees and seedlings. The viral genome is a single stranded (+)RNA about 8,000 nt in size, 6,500 nt of which have been sequenced starting from the polyadenylated 3' terminus. Genomic RNA consists of four open reading frames encoding, in the order from the 5' to the 3' end, the replicationassociated proteins (ORF 1), a 42 kDa putative movement protein (ORF 2), the 46 kDa coat protein (ORF 3), and a 10 kDa protein with nucleic acid binding properties. The genome structure ond organization of FLV-1 resembles that of members of the genus Trichovirus, family Flexiviridae and, indeed, the virus clusters with trichoviruses in phylogenetic trees contructed with the coat protein and the movement protein sequences. However, a distinct difference with all members of the genus rests with the size of the coat protein subunits (46 versus 22-27 kDa) and the presence of ORF 4, which does not occur in all trichovirus genomes.