FIRST REPORT OF APPLE NECROTIC MOSAIC VIRUS INFECTING APPLE TREES IN KOREA

In September 2016, two apple trees (Malus domestica Borkh) of cv. Shinano Sweet showing bright cream spot and mosaic patterns on leaves were observed in Pocheon, South Korea. Mosaic symptoms have been found commonly on leaves of apple trees infected with apple mosaic virus (ApMV). Symptomatic leaves were tested by enzymelinked immunosorbent assay (ELISA) and reverse transcription (RT)-PCR for ApMV but this virus was not detected in either of the samples. Apple necrotic mosaic virus (ApNMV) is a recently described novel ilarvirus isolated from apple trees in Japan and China (Noda et al., 2017) and correlated with a mosaic disease similar to that caused by ApMV. The presence of ApNMV was confirmed by RT-PCR with specific primer pairs ApNMV-CP+1 and ApNMV-CP-1 (Noda et al., 2017). Expected PCR fragments of ca. 650 bp were amplified and directly sequenced. BLASTn results showed 94% nucleotide sequence identity with the CP gene region of the previously published ApNMV (LC108995). The consensus sequence of Korean strain KO (LC276940) was deposited in GenBank. The ApNMV-positive samples were also infected with apple chlorotic leaf spot virus (ACLSV), apple stem grooving virus (ASGV) and apple stem pitting virus (ASPV) as detected by RT-PCR (Han et al., 2016). To our knowledge, this is the first report of ApNMV infecting apple trees in Korea. Further research is needed to establish the relationship between ApNMV and ApMV causing mosaic disease on apple trees.