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Justification for qualification based on EPPO PM 4 Standards
Justification for disqualification
Additional or non-conclusive information
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NAME OF THE ORGANISM: Blackcurrant yellows agent (BKY000)

GENERAL INFORMATION ON THE PEST

Name as submitted in the project specification (if different):

Pest category:

Viruses and viroids

1- Identity of the pest/Level of taxonomic listing:

Is the organism clearly a single taxonomic entity and can it be adequately distinguished from other entities of the same rank?

Is the pest defined at the species level or lower?:

Can listing of the pest at a taxonomic level higher than species be supported by scientific reasons or can species be identified within the taxonomic rank which are the (main) pests of concern?

Not relevant: Fruits (including hops) sector

If necessary, please list the species:

Is it justified that the pest is listed at a taxonomic rank below species level?

Not relevant

Conclusion:

Not candidate: Fruits (including hops) sector

Justification (if necessary):

Black currant yellows disease was found in a single English nursery (Posnette, 1952) and subsequently in several plantations established with bushes distributed from it. The disease, a yellowish-green mottle affecting large sectors of whole laminae, has not been reported in other countries. The disease has only been graft-transmitted between black currants, and different cultivars react similarly to infection. No natural vector has been found, and experimental tests with five aphid species were unsuccessful (Cropley et al., 1964; Thresh, 1987). There is no information on the properties of the causal agent, not listed on ICTV and no sequence available at GenBank. With hindsight and based on the mite observations by Cropley et al., (1964) black currant yellows is most likely associated with black currant reversion virus (cited from Tzanetakis et al., submitted).
When responding to the questionnaire, no counry supported its recommendation for regulation as an RNQP. LT and NL supported its delisting from EU regulation because of no clear identity and absence of isolates.
Certification in the future should focus on the absence of specific virus-like pathogens (viruses, viroids, phytoplasmas) rather than on symptoms of diseases where the pathogen and its sequence data are unknown and not reported for decades but presented in the certification schemes. It is also likely that biological indexing of basic fruit propagation material on indicator plants will be replaced in the future by next generation sequencing analysis (ICVF, 2023). However, using HTS will not provide information on biological relevance.

Blackcurrant yellows agent fulfils the description of phantom agent: Phantom agents have been associated with symptomatic plants and diseases of unknown etiology. Most phantom agents are presumed to be of viral nature, yet (i) neither infected plant material nor reference isolates are available, and (ii) no sequence information is accessible (Tzanetakis et al., submitted).
Due to the lack of isolate, infected material and sequence information, the causal agent of this disease will never be confirmed to be e.g. black currant reversion virus. It should be removed from the RNQP list.

2 – Status in the EU:

Is this pest already a quarantine pest for the whole EU?

Presence in the EU:

List of countries (EPPO Global Database):

Conclusion:

Justification (if necessary):

HOST PLANT N°1: Ribes (1RIBG) for the Fruits (including hops) sector.

Origin of the listing:

Commission Implementing Directive (EU) 2014/98/EU and Commission Implementing Regulation (EU) 2019/2072

Plants for planting:

Plants intended for planting

3 - Is the pest already listed in a PM4 standard on the concerned host plant?

Yes

Conclusion:

Justification (if necessary):

Listed in Standard PM 4-9 Certification scheme for Ribes as 'Black currant yellows'. The pest is not qualified as an RNQP since taxonomy needed to be checked.

4 - Are the listed plants for planting the main* pathway for the "pest/host/intended use" combination? (*: significant compared to others):

Yes

Conclusion:

Justification:

see first observations from Posnette (1952)

5 - Economic impact:

Are there documented reports of any economic impact on the host?

Justification:

Infected bushes are stunted and their crop is greatly reduced (Cropley et al. 1964), but infection is not sufficiently widespread to cause serious economic losses (Thresh, 1987).

What is the likely economic impact of the pest irrespective of its infestation source in the absence of phytosanitary measures? (= official measures)

Is the economic impact due to the presence of the pest on the named host plant for planting, acceptable to the propagation and end user sectors concerned?

Is there unacceptable economic impact caused to other hosts (or the same host with a different intended use) produced at the same place of production due to the transfer of the pest from the named host plant for planting?

Conclusion:

Justification:

6 - Are there feasible and effective measures available to prevent the presence of the pest on the plants for planting at an incidence above a certain threshold (including zero) to avoid an unacceptable economic impact as regards the relevant host plants?

Conclusion:

Justification:

7- Is the quality of the data sufficient to recommend the pest to be listed as a RNQP?

Conclusion:

Justification:

CONCLUSION ON THE STATUS:

Disqualified: no clear taxonomy

8 - Tolerance level:

Is there a need to change the Tolerance level:

Yes

Proposed Tolerance levels:

Delisting

9 - Risk management measures:

Is there a need to change the Risk management measure:

Yes

Proposed Risk management measure:

Delisting

REFERENCES:

Cropley R, Posnette AF & Thresh JM (1964) The effects of black-currant yellows virus and a strain of reversion virus on yield. Annals of Applied Biology, 54: 177–182. doi:10.1111/j.1744-7348.1964.tb01181.x
Thresh JM (1966) Virus diseases of black currants. Report East Mailing Research Station for 1965, 158-163. http://www.isppweb.org/icpve/thresh/Virus%20diseases%20of%20black%20currants.pdf (accessed online 10-16 January 2017)
ICVF (2023) 25th International Conference on Virus and other graft transmissible diseases of Fruit crops (ICVF). 'Let's keep our fruits healthy'. Book of abstracts. Wageningen, 9-13 July 2023.
Posnette AF (1952) New virus diseases of Ribes. East Mailing Research Station, Report for 1951, pp. 133-135.
Tresh JM (1987) Black currant yellows. In Virus diseases of small fruits (No. 631) (ed Converse RH). US Department of Agriculture, Agricultural Research Service pp. 140-141.
Tzanetakis IE, Aknadibossian V, Špak J, Constable F, Harper SJ, Hammond J, Candresse T, Folimonova SY, Freitas-Astúa J, Fuchs M, Jelkmann W, Maliogka VI, Marais A, Martin RR, Mollov D, Vidalakis G, Aboughanem-Sabanadzovic N, Al Rwahnih M, Alabi OJ, Alioto D, Atanda HY, Bagi F, Baranwal VK, Barbosa C, Bar-Joseph M, Belien T, Benítez-Galeano MJ, Bennypaul H, Bertaccini A, Bester R, Blouin AG, Blystad D-R, Botermans M, Bozan O, Brakta A, Brans Y, Bulajić A, Caglayan K, Catara A, Choueiri E, Cieślińska M, Cook G, Craddock I, Cui W, da Graça J, Davino S, Delmiglio C, Dewdney M, Di Serio F, Diaz-Lara A, Digiaro M, Djelouah K, Donovan N, Druciarek TZ, Duran-Vila N, Elçi E, Esquivel-Fariña A, Fall ML, Figueroa J, Fiore N, Fowkes AR, Fox A, Fránová J, Fuchs R, Gaafar YZA, García ML, Ghosh D, Girardi E, Glasa M, Gomez Talquenca S, Gratz A, Gritsenko D, Hajeri S, Hajizadeh M, Hamborg Z, Ho T, Holeva M, Holkar SK, Horner M, Hurtado-Gonzales OP, Ippolito A, Isac V, Iwanami T, Jofre-y-Garfias AE, Jordan R, Katis N, Koloniuk I, Konings H, Križanac I, Krueger R, Kyrychenko A, Laranjeira F, Levy A, Licciardello G, Lu Q-Y, MacFarlane SA, Marcone C, Maree HJ, Margaria P, Martić A, Massart S, Mathioudakis MM, Matić S, Mavric Plesko I, Meekes ETM, Mehle N, Melzer MJ, Meng B, Menzel W, Miljanić V, Minafra A, Minutolo M, Mitra A, Moreno P, Navarro L, Navarro B, Nerva L, Okić A, Olmos A, Onelge N, Osundahunsi B, Palacios MF, Pallas V, Panno S, Perez-Egusquiza Z, Poudel-Ward B, Radišek S, Ramos-González PL, Ramteke P, Ranabhat NB, Rivarez MPS, Rivas F, Roenhorst A, Roy A, Ruiz-García AB, Sabanadzovic S, Šafářová D, Saldarelli P, Salem N, Sanahuja Solsona G, Schoen R, Sharma SK, Shilts T, Sierra-Mejia A, Singh S, Skelton A, Škorić D, Stainton D, Štajner N, Starović M, Stuchi E, Svoboda P, Tahzima R, Tang J, Tessitori M, Thermoz J-P, Thompson E, Thompson J, Trebicki P, Turina M, Ulubas Serce C, Umble J, Valiunas D, Varallyay E, Varma A, Varveri C, Vasquez-Gutierrez U, Vazquez-Iglesias I, Veerakone S, Villamor DE, Vives MC, Vončina D, Wang J, Wenxing X, Westenberg M, Wetzel, T, Winter S, Wright G, Wulff NA, Xu Dong F, Ya Feng D, Yokomi R, Zhou C, Zikeli K, Zindović J (submitted) Streamlining global germplasm exchange: Integrating scientific rigor and common sense to exclude phantom agents from regulation.