First report of Plum pox virus strain M in Japan.
In June 2016, some Japanese apricots (Prunus mume) and apricot (Prunus armeniaca) trees were found with typical Plum pox virus (PPV) symptoms such as ringspot and mottle on leaves, along with some peach (Prunus persica) trees with mild mottle on leaves, in Yokohama, Japan. These trees were distributed in a small area in Yokohama city. Most of them were grown in home gardens, and some were on roadsides, parks, and orchards. The ages of these trees varied, ranging from those estimated to be ∼5 years old to 20 years or more. PPV immunochromatography gave positive results on 133 samples. Further tests were carried out, such as reverse transcription PCR, double antibody sandwich indirect ELISA, direct genome sequencing and phylogenic analysis based on CP gene sequence, which revealed the presence of PPV-M in the samples. Among the 133 ELISA positive samples, the proportions of P. mume, P. persica and P. armeniaca were 114 (85.7%), 3 (2.2%) and 15 (11.2%), respectively, and one (0.75%) was Prunus tomentosa. This is thought to be the first detection of PPV-M in Japan. The relevant area was added to the national eradication programme in February 2017.