Incidence of cymbidium mosaic, odontoglossum ringspot, and orchid fleck virus in orchids in Minnesota and production of antibodies for use in ELISA to detect orchid fleck virus

Abstract

Ninety-six symptomatic orchids representing 36 genera from seven orchid collections, including two conservatories, in Minnesota, USA were tested for cymbidium mosaic virus (CymMV), odontoglossum ringspot virus (ORSV), and orchid fleck virus (OFV) using dipsticks (CymMV and ORSV), RT-PCR (OFV), and transmission electron microscopy (all viruses). CymMV was identified in 22% of the samples, OFV was identified in 17% of the samples, and ORSV was detected in 6% of the samples. Five percent of samples were infected with both CymMV and ORSV and 1% of samples were infected with both OFV and ORSV. Characteristic orchid virus symptoms of chlorotic and necrotic patterns were observed for the majority of infected orchids. Polyclonal antibodies were produced against Escherichia coli expressed OFV phosphoprotein (OFV P) and evaluated for use in plate trapped antigen-enzyme linked immunosorbent assay (PTA-ELISA). After an overnight incubation with PNPP the OFV P polyclonal antisera diluted from 1:1000–1:20,000 (v/v) readily differentiated between fresh healthy and OFV infected orchid (Phalaenopsis hybrid) tissue diluted from 1:5–1:20 (w/v). The high incidence of viruses detected in orchids (50%) suggests limited use of certified virus-free propagation stock and highlights the importance of sanitation to prevent transmission between plants.