Serological detection of Cymbidium mosaic and Odontoglossum ringspot viruses in orchids with polyclonal antibodies produced against their recombinant coat proteins

Cymbidium mosaic and Odontoglossum ringspot viruses infecting orchids were identified by coat protein (CP) properties. The Cymbidium mosaic virus (Cym-MV) CP gene is 672 nt long, potentially encoding 223 amino acids (aa). The Odontoglossum ringspot virus (ORSV) CP gene is 477 nt long, potentially encoding 158 aa. The CP gene of CymMV and ORSV isolates originating from different locations was highly conserved both at the nucleotide and amino acid levels (94-100%). Polyclonal antibodies against CymMV and ORSV were separately produced using bacterially expressed recombinant CP as immunogens. Antisera to CymMV (titre 1: 2000) and ORSV (titre 1: 250) detected the viruses by direct antigen-coated enzymelinked immunosorbent assay (DAC-ELISA) in orchid samples collected from Sikkim, India. Survey results indicated the prevalence of mixed infection of CymMV and ORSV in Cymbidium spp. The immunoreagents we developed will be useful for virus indexing in orchid certification programmes.