First report of Hop latent viroid (HLVd) in China

Xinjiang is the primary region of hop (Humulus lupulus) production in China due to high quality and productivity promoted by the favorable climate, geography and soil type. Hop latent viroid (HLVd) does not cause any obvious symptoms in hop but results in a serious decrease in the content of alpha acid, an important characteristic for use in the beer industry (Matoušek et al. 2001). In September 2006, 96 samples were gathered from symptomless hop leaves in commercial fields in the Wensu, Yanqi, Changji, Shawan, Emin, Tacheng and Yili districts of Xinjiang, China. Total RNA was extracted and subjected to dot blot hybridization using a biotin-labeled HLVd cDNA probe and also RT-PCR, using a pair of oligonucleotide primers HLVdR (5¢-CCACCGGGTAGTTTCCAACT-3¢) and HLVdF

(5¢-ATACAACTCTTGAGCGCCGA-3¢) specific for HLVd (Matoušek et al. 2001). Dot blot hybridization results demonstrated that HLVd was present in all surveyed regions with an infection rate in each sample between 56% and 88%. Using RT-PCR, a 256-bp DNA fragment was amplified from 16 samples collected from seven different regions. The amplified products were cloned into a pGM-T cloning vector (Tiangen) and sequenced (GenBank Accessions EF613181 to EF613192). Sequence comparisons revealed 99.2% to 100% homology among the collected isolates and with the HLVd sequences previously reported in GenBank. To our knowledge, this is the first report of HLVd from China. Considering the poor quality of hops infected with HLVd, our results show the need for a domestic eradication program to control the spread of this viroid.