Detection by RT‐PCR of Cymbidium Mosaic Virus in Orchids

The cymbidium mosaic potexvirus (CyMV) coat‐protein gene was selected for the design of oligonucleotide primers. Reverse transcription‐polymerase chain reaction (RT‐PCR) was performed with 20‐mer CyMV coat‐protein‐specific primers to amplify a 692 base‐pair fragment from crude nucleic acid extracts of virus‐infected orchid‐leaf tissue. The lowest concentration of template viral RNA required to detect the virus was 10 fg. No PCR products were obtained when odontoglossum ringspot virus (ORSV) RNA orextracts of healthy Cymbidium sp. were used as templates in RT‐PCR using the same primers. A 2μl aliquot of crude nucleic‐acid extracts from 0.1 g of the CyMV‐infected leaf tissue was sufficient to yield a diagnostic PCR product.