Complete genome sequence and comparative analysis of grass carp reovirus strain 109 (GCReV-109) with other grass carp reovirus strains reveals no significant correlation with regional distribution

A new grass carp reovirus strain, tentatively named GCReV-109, was isolated in Hubei, China, and its complete genome sequence was determined. The genome contained 11 double-stranded RNA segments (S1-S11) covering 24,620 base pairs. All of the segments had conserved terminal nucleotides, with GUAA(U)/U-C at the 5' end and UCAUC at the 3' end. Protein sequence comparison showed that GCReV-109 was most closely related to GCRV-GD108 and shared 96.6-99.5 % protein sequence identity but only shared 16.7-46.1 and 15.1-45.4 % identity with GCRV-873 and HGDRV, respectively. Phylogenetic analysis showed that grass carp reovirus strains in China can be divided into three genotypes. Further analysis revealed homology between the GCRV-109 VP56 and HGDRV VP55 proteins, as well as GCReV-109 NS38, GCRV-873 NS38, and HGDRV VP39. The results of these comparisons also indicated that the homology between viruses was not necessarily linked to their geographical distribution. Our study will help in recognizing and understanding the genome structure and genetic diversity of grass carp reovirus.