Molecular characterization and specific detection of two genetically distinguishable strains of East Asian Passiflora virus (EAPV) and their distribution in southern Japan.

The Ibusuki (IB) strain of the East Asian Passiflora virus (EAPV) causes mottling of fruit when it infects passionfruit, but not malformation or woodiness, unlike the Amami-O-shima (AO) strain, and the host range for these two strains are different. We determined the complete nucleotide sequence of the IB strain, and a comparison with that of the AO strain revealed the great diversity of the 5'-terminal region of the IB strain's genome (5' UTR and P1 gene). The involvement of these regions in the different symptoms on fruit and host range was suggested. The neighbor-joining tree constructed using the nucleotide sequences of coat protein gene of eight EAPV isolates including those from abroad showed the independent position of the IB strain, and that constructed using the whole ORFs also showed distant relationships between the AO and IB strains. We investigated the distribution of the two strains in southern Japan from 2005 to 2010. The AO strain was detected in the samples from AO at all periods, and its emergence was also observed in the Kagoshima mainland in 2005. In contrast, the IB strain is restricted to the Kagoshima mainland, and the distribution survey revealed that this strain is now extinct even in this region, indicating the uniqueness of the IB strain in terms of sequence properties and geographical distribution.