First report of Hop stunt viroid from peach (Prunus persica) with dapple fruit symptoms in China

Hop stunt viroid (HSVd) was first described from hops with stunt disease in Japan. HSVd belongs to the genus Hostuviroid, family Pospiviroidae, and has the broadest host range known for any viroid. It infects many fruit crops including peach, plum, pear, citrus and grapevine (Shikata, 1990). HSVd has been isolated from peaches with dapple fruit disease in Japan (Sano et al., 1989). Peaches (Prunus persica) are one of the oldest stone-fruits grown in China and are widely planted. Dapple fruit disease of peaches is very common in China, being seen almost everywhere in Chinese fruit markets and has been presumed to be due to infection with HSVd. However, to date there has been no report of the isolation of HSVd from peach in China.

To clear up the relationship between viroid and dapple symptoms on peach, a sample (var. Xiangshanhong) showing symptoms of dapple fruit disease (Fig. 1) was obtained in July 2005 from Tianxiu fruit market in the Haidian district of Beijing, People's Republic of China. Nucleic acids were extracted (Li et al., 1995) and used for reverse transcription-polymerase chain reaction (RT-PCR) (Hassan et al., 2004). A 297bp DNA fragment was amplified from the sample by RT-PCR using primers R1 (5'-GCTGGATTCTGAGAAGAGTT-3') for RT, and R2 (5'-AACCCGGGGCT CCTTTCTCA -3') and F1 (5'-AACCCGGGGCAACTCTTCTC-3') for PCR; R2 and F1 both include SmaI sites (Hassan et al., 2004). Amplified products were cloned into pGEM-T (Promega, Madison, USA) and positive clones selected by digestion with SmaI. Four clones were sequenced. Two clones were identical to database sequence D13764, obtained from an isolate of HSVd from peach in Japan (Sano et al., 1989), while the other two clones each differed from this by a single nucleotide (A25→G or G107→A). These results show that the isolate obtained from peach in China is closely-related to HSVd from dapple fruit disease affected peaches in Japan (Sano et al., 1989). This is the first report of HSVd-peach in China. Many varieties of peach are grown in China but ongoing investigations should soon make the distribution of HSVd in peach in this country clear.