First report of Hop stunt viroid on hop in Slovenia
Since 2007, symptoms resembling those of Hop stunt viroid (Pospiviroid, HSVd) have been observed in several hop gardens located in the Savinja valley and Koroška region in Slovenia. Symptoms were observed on different cultivars (Humulus lupulus cvs. ‘Celeia’, ‘Bobek’ and ‘Aurora’) and included stunting, leaf curl, small cone formation and dry root rot. In 2007, the disease incidence varied from 1 to 30% and increased rapidly (by up to 10%) each subsequent year, predominantly along plant rows. Laboratory analysis (RT-PCR, sequencing) confirmed the presence of HSVd in leaf and cone samples (H. lupulus cv. ‘Celeia’) collected from two different hop gardens. Five different sequences were obtained and revealed 95-99% sequence identity with various HSVd variants (from grapevine, citrus, and cucumber) recorded in GenBank (NCBI). This is the first time that HSVd is reported on hop in Europe*. Strict phytosanitary measures have been taken in Slovenia to eradicate the disease and prevent any further introduction. Surveys are being carried out in hop gardens to determine the extent of the disease. Eradication measures include: destruction of infected plants (uprooting and burning) and those in their close vicinity, prohibition to grow HSVd host plants on infected sites for 2 years, and prohibition to move plant waste from the infected areas to hop gardens. Detailed maps showing the infected areas can be viewed on the website of the Slovenian NPPO: http://www.fu.gov.si/en/services_and_measures/regulated_organisms/hop_stunt_viroid
The situation of Hop stunt viroid in Slovenia can be described as: Present, first observed in hop gardens in 2007 in the Savinja valley and Koroška region, under eradication.
* Until the 1980s, hop stunt was only known to occur in Japan but the disease was then reported in hop gardens in the Republic of Korea (Lee ; Choi, 1988), China (Xinjiang province, Guo et al., 2008), and the USA (Washington state, Eastwell ; Nelson, 2007).
NPPO of Slovenia (2012-02).
Radisek S, Majer A, Jakse J, Javornik B, Matoušek J (2012) First report of Hop stunt viroid infecting hop in Slovenia. Plant Disease 96(4), p 592.
Eastwell KC, Nelson ME (2007) Occurrence of viroids in commercial hop (Humulus lupulus L.) production areas of Washington State. Plant Management Network, 7 pp. https://sharepoint.cahnrs.wsu.edu/hops/Shared
Guo L, Liu S, Wu Z, Mu L, Xiang B, Li S (2008) Hop stunt viroid (HSVd) newly reported from hop in Xinjiang, China. Plant Pathology 57(4), p 764.
Lee JY, Choi JK (1988) Detection of Hop stunt viroid in Korea. Korean Journal of Plant Pathology 4(3), 234-237.