Archivio Journal of Plant Pathology

Abstract:

Two double stranded RNA (dsRNA) segments, ca. 1.7 and 2.0 kbp in length, were extracted from leaf tissues of a pittosporum plant (Pittosporum tobira), infected by the nucleorhabdovirus Eggplant mottled dwarf virus (EMDV), which showed yellowing, chlorotic vein banding and mottling of the leaves. DOP-PCR products obtained using denatured dsRNA preparations as template showed high sequence similarity to viruses of the family Partitiviridae. Computer-assisted analysis of a sequenced 676 bp fragment showed it to be part of an RdRp gene with high identity at the amino acid level with comparable gene fragments of different alphacryptoviruses, i.e Pepper cryptic virus 1 (PCV-1, 78%), Black raspberry cryptic virus (BRCV, 67%), Pyrus pyrifolia virus (PpV, 64%) and Beet cryptic virus 3 (BCV-3, 58%). In a phylogenetic tree constructed with partial RdRp amino acid sequences, the pittosporum virus grouped with species of the genus Alphacryptovirus and unassigned viruses of the family Partitiviridae. RT-PCR with specific primers designed based on the RdRp sequence detected the virus in 2 of 50 pittosporum plants, both showing chlorotic vein banding symptoms, differing from the vein yellowing induced by EMDV alone. The present results show that pittosporum hosts a putative alphacryptovirus for which the name of Pittosporum cryptic virus 1 (PiCV-1) is proposed.