NAME OF THE ORGANISM: Tobacco necrosis virus (Tobacco necrosis necrovirus) (TNV000)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different to the preferred name):
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?
Yes
Is the pest defined at the species level or lower?:
Yes
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: Seed potato sector
Is it justified that the pest is listed at a taxonomic rank below species level?
Not relevant
Conclusion:
- Not evaluated: Seed potato sector
Justification (if necessary):
Recently, TNV has been split in two viruses TNV-A and TNV-D of which TNV-D has been shown to infect potatoes naturally, while the host status of potato for TNV-A is uncertain. The virus is transmitted by zoospores of the soil-borne fungus Olpidium brassicae. However, transmission by seed potatoes has never been shown (FAO/IPGRI, 1998 Technical Guidelines for the Safe Movement of Germplasm No 19. Potato. (ed. Jeffries CJ) pp 84-85) and transmission was not obtained in an experiment using infected seed potatoes (Anonymous, 1931, Verslagen en Mededelingen van den Plantenziektenkundigen Dienst te Wageningen, No. 64 page 84). Thus, seed potato has not been shown to be a pathway for TNV-D and, therefore TNV-D does not seem to qualify for the RNQP-status. However there has been limited research so far on these viruses and their hosts. Possible other viruses may be involved in the disease observed. Therefore experts recommended to follow the EPPO PM 4 Standard on seed potatoes (continue to list TNV), which revision (including resolving any taxonomic issues) could be done when revising the EPPO PM 3/21(2) Standard on post-entry quarantine for potato.
2 – Status in the EU:
Is this pest already a quarantine pest for the whole EU?
No
Presence in the EU:
Conclusion:
not evaluated
HOST PLANT N°1: Solanum tuberosum (SOLTU) for the Seed potato sector.
Origin of the listing:
PM 4/28 (1)
Plants for planting:
Plants intended for planting of nuclear stock, other than [true] seeds
3 - Is the pest already listed in a PM4 standard on the concerned host plant?
Yes
Conclusion:
Qualified
Justification (if necessary):
Experts agreed that the nuclear stock should be tested or derived from mother plants which have been tested for this virus.
CONCLUSION ON THE STATUS:
Recommended for listing as an RNQP, based on EPPO PM 4 Standard, only for the nuclear stock.
8 - Tolerance level:
Is there a need to change the Tolerance level:
Yes
Proposed Tolerance levels:
Zero tolerance, only for nuclear stock.
9 - Risk management measures:
Is there a need to change the Risk management measure:
Yes
Proposed Risk management measure:
Nuclear stock should be tested or derived from mother plants which have been tested for Tobacco necrosis virus.
REFERENCES: