The 1.8-kb nucleotide sequences from the three symptomatic
hydrangeas had 100 % identity with each other.
The sequence was deposited in the GenBank database
under accession number AB738736. Unexpectedly, the
sequence had only 95.6 % identity with ‘Ca. P. japonicum’
strain JHP at the nucleotide level. Conversely, the sequence
showed more than 97.5 % nucleotide identities, the
threshold criterion for classification of ‘Candidatus Phytoplasma’
species (Firrao et al. 2004), with all previously
described ‘Ca. P. asteris’ including hydrangea phyllody
phytoplasmas reported in Europe: 99.9 % identity with
strain HYPh and 99.5 % identity with strain HYDP
(Table 1). Furthermore, the sequence shared a significantly
high identity of 99.9 % with some ‘Ca. P. asteris’ strains
detected from plants other than hydrangea: strain RhY
from Rhus javanica in Gunma Prefecture, Japan; strain
SWB from R. javanica in Korea; strain OY-M from onion
in Japan; strain MD from mulberry trees in Korea; strain
MYD-AnH from mulberry trees in China; strain AlfS-L
(GU289675) from alfalfa in Lithuania; strain PrG from
primula; Sasa witches’-broom phytoplasma (AB293421) in
Korea; Silene nicaeensis virescence phytoplasma
(EF570134) in Italy; strain AshY (AY566302) from ash in
Korea; and epilobium phyllody phytoplasma (AY101386)
in Estonia. These results suggest that the phytoplasma
infecting the symptomatic hydrangeas in Gunma Prefecture
is not a strain of ‘Ca. P. japonicum’, that is widely distributed
in hydrangeas Japan, but belongs to ‘Ca. P.