‘Zipi Fengdou’ is a restorative food made of the stem of Dendrobium devonianum, Paxt., whose high commercial value presents the constant risk of adulteration with cheaper ‘Foudou’ products made from other Dendrobium species. Therefore, this study developed two assays capable of detecting D. devonianum based on SYBR Green II and TaqMan probe real-time PCR. By performing the diagnostic real-time PCR based on SYBR Green II, two DNA fragments (163 and 159 bp) were specifically amplified from the internal transcribed spacer (ITS) region of D. devonianum. The average cycle threshold (Ct) values of two D. devonianum samples collected from different Chinese provinces were shown to be 16.65 for ITS1–4 and 16.38 for ITS2–1, which were significantly (P < 0.001, SPSS) different from those of the reference Dendrobium species used as adulterants of ‘Zipi Fengdou’ (34.94 for ITS1–4, 34.67 for ITS2–1). Moreover, in the assay based on TaqMan probe real-time PCR, two TaqMan probes were designed and tested for the quantitative detection of D. devonianum in commercial samples labelled as ‘Zipi Fengdou’. As a result, this assay specifically and sensitively distinguished the processed Fengdou' sample of D. devonianum from those of adulterant Dendrobium species.
The real-time PCR assay based on both SYBER GREEN II and TaqMan probe that is reported here is specifically and sensitively in detecting D. devonianum from those of adulterant Dendrobium species. Furthermore, real-time PCR assay based on TaqMan probe can be used to determine the content of D. devonianum in medicine or healthcare products.