Homology differences between complete Sacbrood virus genomes from infected Apis mellifera and Apis cerana honeybees in Korea.

Sacbrood virus (SBV) represents a serious threat to the health of managed honeybees. We determined four complete SBV genomic sequences (AmSBV-Kor1, AmSBV-Kor2, AcSBV-Kor3, and AcSBV-Kor4) isolated from Apis mellifera and Apis cerana in various regions of South Korea. A phylogenetic tree was constructed from the complete genomic sequences of these Korean SBVs (KSBVs) and 21 previously reported SBV sequences from other countries. Three KSBVs (not AmSBV-Kor1) clustered with previously reported Korean genomes, but separately from SBV genomes from other countries. The KSBVs shared 90-98 % identity, and 89-97 % identity with the genomes from other countries. AmSBV-Kor1 was least similar (~90 % identity) to the other KSBVs, and was most similar to previously reported strains AmSBV-Kor21 (97 %) and AmSBV-UK (93 %). Phylogenetic analysis of the partial VP1 region sequences indicated that SBVs clustered by host species and country of origin. The KSBVs were aligned with nine previously reported complete SBV genomes and compared. The KSBVs were most different from the other genomes at the end of the 5' untranslated region and in the entire open reading frame. A SimPlot graph of the VP1 region confirmed its high variability, especially between the SBVs infecting A. mellifera and A. cerana. In this genomic region, SBVs from A. mellifera species contain an extra continuous 51-nucleotide sequence relative to the SBVs from A. cerana. This genomic diversity may reflect the adaptation of SBV to specific hosts, viral cross-infections, and the spatial distances separating the KSBVs from other SBVs.