Quantitative detection of Cymbidium mosaic virus by real time PCR

The technique of SYBR Green-based quanti-tative real-time reverse transcription polymerase chain reaction (real-time RT-PCR) was applied to quantitative detect a 764 bp nucleotide sequence containing total coat protein (cp) gene of Cymbidium mosaic virus (CyMV). The plasmid containing the target sequence was con-structed to prepare the standard curve and detect the sensitivity. The standard curve was drawn based on the linear relationship between the logarithm (base 10) of the quantity of target sequence and cycle threshold [C(T)]. While the concentration of plasmid DNA falling within the range of 2.6×107 to 2.6×102 copies per tube established a regression equation, y=-0.3583x+10.32, and related coefficient: r2=0.995. The real-time RT-PCR assay for CyMV had a minimum detectable quantity of two copies per tube. The naturally infected samples of Phalaenopsis sp. and the artificially inoculated samples ofArachnis sp. with trace CyMV were quantitatively detected using this method. CyMV in the positive samples of Phalaenopsis sp. and Arachnis sp. was confirmed by DNA sequencing and cp gene homeology blast. The results showed that CyMV extracted from the leaves of orchid in Hangzhou, Zhejiang Province, China, could be derived from Kunming city (KM), Yunnan Province, China. This method characterized by high sensitivity, specificity, and precision is suitable for early diagnosis and quantitative detection of CyMV.