Arch Virol (2001) 146: 1125–1137 Sequence comparison and phylogenetic analysis of fish nodaviruses based on the coat protein gene * L. Dalla Valle 1 , E. Negrisolo 1 , P. Patarnello 3 , L. Zanella 2 , C. Maltese 4 , G. Bovo 4 , and L. Colombo 1 1 Dipartimento di Biologia, Università di Padova, Padova, Italy 2 Veneto Agricoltura, Polo Tecnologico Agripolis, Legnaro, Italy 3 Dipartimento di Scienze della Produzione Animale, Università di Udine, Udine, Italy 4 Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Italy Accepted November 27, 2000 Summary. We have amplified by reverse transcription-polymerase chain reaction (RT-PCR) and sequenced a 605-bp fragment covering the variable region of the coat protein gene of fish nodaviruses infecting European sea bass, Dicentrarchus labrax (n = 24), and shi drum, Umbrina cirrosa (n = 2), in the Mediterranean basin. Nine new isolates were identified and their sequences were combined with se- quences in the literature to produce three different data sets. The first set, based on amino acid sequences, was used to verify the monophyly of fish nodaviruses. The second and third data sets, based on nucleic acids, were used to resolve the phylo- genetic relationships between closely related fish nodaviruses. Phylogenetic anal- yses were performed according to the maximum parsimony and neighbor-joining methods. Our results support the monophyly of fish nodaviruses. Moreover, they confirm the subdivision of fish nodaviruses into four main clusters, in agreement with the previously suggested phylogeny of the genus Piscinodavirus, that was based on a smaller number of sequences and an alternative phylogenetic approach [14]. All the Mediterranean isolates were clustered in the group of the red-spotted grouper nervous necrosis virus and appear to have a restricted geographic distri- bution, except for one sequence-type (10 samples) that is widespread throughout the basin. * The new sequences presented in this paper have been submitted to the EMBL data bank where they are available under the accession numbers AJ277803–AJ277811.