Two grapevine viroids in China and the possible detection of a third.
A survey was conducted during 2002-05 to identify viroids affecting grapes in China. Leaves were harvested in June from 70 samples, comprising 7 wild plants from Liaoning, 58 cultivars in a grapevine nursery in Beijing, 2 from Xinjiang autonomous region and 3 from Hebei. Nucleic acids were extracted and tested for the presence of 4 grapevine viroids by dot-blot or northern hybridization using digoxygenin-labelled riboprobes for Hop stunt viroid (HSVd), Apple fruit crinkle viroid (AFCVd), Grapevine yellow speckle viroid (GYSVd) and Citrus exocortis viroid (CEVd). HSVd was detected in 41 samples, GYSVd in 29 and AFCVd in one. CEVd was not detected. Twenty-three samples were infected with both HSVd and GYSVd, and one with the Australian grapevine viroid (AGVd)-like viroid, HSVd and GYSVd. Infection in 13 samples positive by dot-blot hybridization for HSVd and 12 for GYSVd was confirmed by RT-PCR. The identities of the viroids were confirmed by sequencing the PCR products obtained. Infection of the sample positive when using the AFCVd probe could not be confirmed by RT-PCR using primers that should detect AGVd. At present the identity of the viroid of this sample is uncertain. GYSVd has been reported from China previously but based solely on symptoms. This is thought to be the first report confirmed by other tests and the first report of HSVd in grapes in China.