Molecular Characterization and Survey of the Infection Rate of Orchid fleck virus in Commercial Orchids

Kim, Sung Ryul; Yoon, Ju Yeon; Choi, Gug Sun; Chang, Moo Ung; Choi, Jang Kyung; Chung, Bong Nam

The Plant Pathology Journal 2010;26(2):130-138.
Published online June 30, 2010.

Molecular Characterization and Survey of the Infection Rate of Orchid fleck virus in Commercial Orchids

Sung Ryul Kim, Ju Yeon Yoon, Gug Sun Choi, Moo Ung Chang, Jang Kyung Choi, Bong Nam Chung

Abstract

Orchid fleck virus (OFV) is an unassigned plant virus in the family Rhabdoviridae. OFV was isolated from Cymbidium sp. showing oval necrotic lesions on their leaves in Korea, and designated as OFV-NHHS1. The complete nucleotide sequence of the RNA1 (6,413 nt) (GenBank accession no. AB516442) and RNA2 (6,001 nt) (GenBank accession no. AB516441) was determined in this study. RNA1 and RNA2 contained five and one ORF respectively. RNA1 encodes nucleocapsid (N) of 49 kDa, ORF2 of 26 kDa, ORF3 of 38 kDa, ORF4 of 20 kDa and glycoprotein (G) of 61 kDa proteins, whereas RNA2 encodes a single polymerase of 212 kDa. OFVNHHS1 shared extremely high similarity of 98.6-100% and 98.9-99.6% in nucleotide and amino acid sequences with a Japanese isolate, OFV-so, respectively. However, the N, G and L of OFV-NHHS1 revealed 6.9-19.3%, 7.3- 12.0%, and 13.4-26.6% identities to those of 29 Rhabdoviruses, respectively. To survey the infection rate of OFV in commercial orchids in Korea, 51 Cymbidium sp., 10 Phalaenopsis sp., 22 Oncidium sp. and 21 Dendrobium sp. plants that showed typical viral symptoms were collected. RT-PCR with specific primers for detection of Cymbidium mosaic virus (CymMV), ORSV and OFV showed high infection rate by ORSV alone and double infection by ORSV and CymMV. One of the orchids tested was infected with OFV. This is the first report of the complete nucleotide sequences of OFV isolated in Korea.

Key Words: Cymbidium sp., CymMV, Orchid fleck virus, Rhabdovirus, ORSV, RT-PCR, sequence analysis