Sequence comparison and phylogenetic analysis of fish nodaviruses based onthe coat protein gene

We have amplified by reverse transcription-polymerase chain reaction (RT-PC R) and sequenced a 605-bp fragment coveting the variable region of the coat protein gene of fish nodaviruses infecting European sea bass, Dicentrarchu s labrax (n = 24), and shi drum, Umbrina cirrosa (n = 2), in the Mediterran ean 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 s et, 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 phylogenetic relationships between closely related fish nodaviruses. Phylogenetic analyses 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 nodavir uses into four main clusters, in agreement with the previously suggested ph ylogeny of the genus Piscinodavirus, that was based on a smaller number of sequences and an alternative phylogenetic approach [14]. All the Mediterran ean isolates were clustered in the group of the red-spotted grouper nervous necrosis virus and appear to have a restricted geographic distribution, ex cept for one sequence-type (10 samples) that is widespread throughout the b asin.