Occurrence of Viroids in Commercial Hop (Humulus lupulus L.) Production Areas of Washington State

Abstract

Viroid status was investigated in commercial hop (Humulus lupulus) plantings in three regions of intensive hop production in Washington State. Hop stunt viroid (HSVd), the causal agent of hop stunt disease, was detected for the first time in hop plants in North America. HSVd was detected in samples from 10 of the 33 hop gardens sampled and in 19 of 126 plant samples. Infection with HSVd was associated with chlorosis and reduced plant vigor. Reverse transcription-polymerase chain reaction amplification, sequence identity, and pathogenicity of hop extracts on cucumber seedlings confirmed the presence of HSVd. Apple fruit crinkle viroid (AFCVd), recently reported in hops in Japan, was not detected by RT-PCR in any samples. Hop latent viroid (HLVd), which is frequently associated with hop germplasm world-wide, was detected with high frequency (98 of 126 hop plants surveyed). Accepted for publication 23 September 2007. Published 27 November 2007.