First report of Citrus bark cracking viroid (CBCVd) on hops (Humulus lupulus)

 

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Publication Date

Tue, 30 Jun 2015, 07:17

Last Updated

June 30, 2015, 7:17 a.m.

Report Number

SVN-06/2

Country

Slovenia

Report Status

Final

Hosts

CBCVd is a highly aggressive viroid on new host: hops Humulus lupulus L.

Geographical Distribution

Slovenia (severe outbreaks on Humulus lupulus; under eradication). Present in Greece, Italy, Israel and Tunisia (on Citrus).

Summary

An unknown and aggressive disease was observed in 2007 in hop gardens in Slovenia. The disease spread extremely rapidly and caused severe stunting and death of affected plants. Diagnostic analysis, which was based on screening for a range of all know hop pathogens, revealed the presence of Hop stunt viroid (HSVd) (Radisek et al., 2012) the causal agent of hop stunt disease (Eastwell and Sano, 2009; Sano, 2003). The new disease in Slovenia corresponds to descriptions of HSVd infections, although some characteristics, such as a shorter incubation period, higher aggressiveness and unreliable RT-PCR detection limited to hop cone tissue, were unusual and atypical for HSVd. Further diagnostic research of symptomatic plants using next generation sequencing analysis revealed the presence of Citrus bark cracking viroid (CBCVd) (Jakse et al., 2014) which, until this finding, had been described as a minor pathogen of citrus plants. Infection tests using a biolistic inoculation technique proved the high aggressiveness and infectivity of CBCVd on hop and, on the basis of this and the results of NGS and RT-PCR testing of samples from all infected hop gardens, CBCVd was recognised as the causal agent of a new viroid disease on hop, named ‘severe hop stunt disease’ (Jakse et al., 2014). Hop is a new and highly susceptible host for CBCVd. The location of outbreaks outside citrus growing areas defines a new and unexpected region for this viroid. The main host plants are Citrus spp., Poncirus trifoliata and, since its discovery in Slovenia, also hop (Humulus lupulus). The main patway are host plants for planting and other plant material, including fruits and contaminated machinery.

Ref.: Jakše J. Radisek S., Pokorn T., Moatoušek J., Javornik B. (2014) Deep-sequencing revealed a CBCVd viroid as a new and highly aggressive pathogen on hop. Plant Pathology; doi: 10.1111/ppa.12325 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), 592.

Danger

CBCVd is very damaging for hops. Severe symptoms have been developed 4 months to 1 year after infection. The incubation period for the development of hop stunt disease caused by HSVd is 3–5 years (Sano, 2003). Disease is spread in a hop garden rapidly in a direction of handling with machinery and tools. Since hop is a perennial plant, which requires an extensive and long term support system for cultivation, infections of hop gardens have a high impact on production and cause high economic damage.

Contact for info

AFSVSPP, Dunajska 22, Ljubljana, [email protected]

Report files

Website

http://www.uvhvvr.gov.si/si/delovna_podrocja/zdravje_rastlin/karantenski_skodljivi_organizmi/posebno_nadzorovani_organizmi/viroidna_zakrnelost_hmelja/

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