PLUM POX VIRUS ISOLATED FROM JAPANESE APRICOT (PRUNUS MUME) IN JAPAN, AND THE DEVELOPMENT OF A RAPID ONE-STEP IMMUNOCHROMATOGRAPHIC ASSAY FOR ON-SITE DIAGNOSIS

For the first time, Plum pox virus (PPV) was detected in Japanese apricot trees (Prunus mume) in Tokyo, Japan. The trees exhibited ringspot and mottles on the leaves, color breaking on the petals, and, occasionally, mild ringspot and malformation on the fruits, which closely resembled the typical symptoms of PPV-infected plum, apricot, and peach trees. The presence of PPV in the diseased trees was confirmed by RT-PCR using specific primers to amplify a 243-bp fragment from the C-terminus of the coat protein coding region. To characterize the isolate of PPV present in Japan, complete nucleotide sequence analysis was performed. The genomic RNA of the Japanese isolate, designated Ou1, was 9,786 nucleotides (nt) long, excluding the 3’-terminal poly(A) tail, and contained a single open reading frame (nt 147-9569). The nucleotide sequence was 98.1-99.4% identical to PPV-D isolates from various other parts of the world. Phylogenetic analysis of the complete nucleotide sequences of the PPV-D isolates revealed that Ou1 was not included in the clusters of the North American isolates. For the nationwide detection of PPV, a one-step immunochromatographic assay was developed based on a polyclonal antibody against the CP of Ou1. This kit enables the rapid detection of PPV within 15 min using infected flowers, young leaves, old leaves, fruit, and dormant wood of Japanese apricot.