Phylogenetic relationship of the full-length glycoprotein (G) sequences of 28 IHNV strains with IHNV 220-90. Genogroups are depicted by vertical lines, as described by . Brackets indicate the three major genogroups, U, M and L. IHNV 220-90 (blue diamond) is grouped under M genogroup. Data of virus isolates used here are available in additional file 1. Phylogenetic tree analysis was conducted by neighbor-joining method using 1000 bootstrap replications. The scale at the bottom indicates the number of substitution events and bootstrap confidence values are shown at branch nodes.