Ampeloviruses associated with incomplete flower syndrome and leaf-edge necrosis in Japanese apricot

Japanese apricot (Prunus mume Sieb. et Zucc.) trees produce popular fruits and are also used in Japan as ornamental flowering trees. Since the 1980s, graft-transmissible symptoms (e.g., incomplete flowers and leaf-edge necrosis) have been observed on ‘Nanko’ trees in Wakayama Prefecture. We here describe the detection of viruses associated with these symptoms in Japanese apricot trees using DECS analysis (i.e., double-stranded RNA [dsRNA] isolation, exhaustive amplification, cloning, and sequencing). We isolated dsRNA from symptomatic flowers, including dsRNA of plum bark necrosis stem pitting-associated virus (PBNSPaV), little cherry virus 2 (LChV-2), and a Luteovirus-like sequence. The reverse transcription polymerase chain reaction results suggested that PBNSPaV and LChV-2 may induce the development of incomplete flowers and leaf-edge necrosis. In contrast, the Luteovirus-like sequence is apparently unrelated to these symptoms. Additional investigations are necessary to clarify the relationship between the symptoms and viral infections.