A novel alphapartitivirus detected in Japanese pear.

Pyrus pyrifolia cryptic virus (PpCV) had been previously reported from Japanese pear (Pyrus pyrifolia). In analyses of Japanese pear, two other double-stranded (ds) RNA molecules (dsRNA4 and 5) were observed along with the three dsRNA segments from PpCV on an electrophoretic profile of isolated dsRNA. When the purified dsRNA sample was deep sequenced by a next-generation sequencer, two de novo assembled contigs corresponding to dsRNA4 and 5, with predicted amino acid sequences showing homologies to the RNA-dependent RNA polymerase and the capsid protein of Rose partitivirus, respectively, were found by BLAST analysis. The relationships between the two contigs and dsRNA4, 5 were confirmed by northern blot analyses with probes amplified using primers designed from the contigs. Terminal sequence analyses by rapid amplification of cDNA ends revealed that dsRNA4 and 5 were 1945 and 1788 bp long, respectively. The 5' terminal sequences (GUCAAAUU) of dsRNA4 and 5 were conserved. Based on genome size and phylogenetic analyses, the newly found virus is thought to be a member of the genus Alphapartitivirus. Thus, it has been designated as Pyrus pyrifolia partitivirus 2.