Tracking Down the Tomato Brown Rugose Fruit Virus

Extraction 1 (photo: Denise Altenbach, Agroscope)
Extraction 1 (photo: Denise Altenbach, Agroscope)

Changins/Wädenswil, 24.05.2022 - The tomato brown rugose fruit virus poses a new threat to Swiss agriculture - especially to tomatoes and peppers. Agroscope is playing a key role in controlling this quarantine organism in Switzerland. A newly created research group diagnoses submitted plant samples in the quarantine laboratory via a PCR test. A positive test result requires tough measures to prevent spread and contain damage: recently, an entire delivery of 6000 seedlings had to be destroyed at Zurich airport.

Films are based on stories like this: a delivery of around 6000 tomato seedlings arrives in Switzerland by aircraft. Inspectors from the Swiss Federal Plant Protection Service (SPPS) take plant samples and send them to Agroscope Changins (canton of Vaud). In a specially secured quarantine laboratory, researchers test the plant samples for the tomato brown rugose fruit virus (ToBRFV). The results, which come back the next day, are positive for ToBRFV. Agroscope reports its findings to the SSPS without delay. The SSPS rules that the entire delivery must be destroyed at the airport.

Global trade on the rise

The case described above is no longer an isolated occurrence. The rise in global trade of seed and planting material has been accompanied by an increase in new pests in Switzerland. Last year, ToBRFV was discovered on imported plants in Switzerland for the first time. So far in 2022 Agroscope has inspected three imports, of which two were positive for the virus. -It’s a race against time- asserts Denise Altenbach, Head of the -Molecular Diagnostics for Controlled Harmful Plant Organisms- Research Group. -We need to send the results of the molecular tests to the airport no later than 48 hours after receipt of the plant samples at the SSPS. We can’t afford to make mistakes. We-ve got to stop infected seedlings from making their way into production farms and home gardens.- The team headed by Denise Altenbach was specially created for such analyses at Agroscope in November 2021. It is still being built up and staff numbers are being further increased.

Up to 1000 samples planned

The SSPS and Agroscope’s Plant Protection Service work closely with the Cantonal Plant Protection Services (CPPSs) to control the tomato brown rugose virus. The three-way cooperation works well to prevent, as far as is possible, the spread of this contagious virus. This objective can only be achieved if the virus is detected at an early stage. This year, it is planned to conduct up to 1000 spot checks on e.g. tomato and pepper production farms as well as in nurseries or garden centres. In addition, there are the non-plannable operations, as with the import described above.

Drainage water also examined

The drainage water from greenhouses is also tested for ToBRFV. This procedure is also applied with the wastewater from sewage treatment plants in the case of Coronavirus. If a sample tests positive e.g. on a production farm, the fruit harvest can continue under strict hygiene measures. This is because experts estimate the risk of transmission of the virus through the fruit as slight, whilst having to destroy a crop would lead to disproportionately high losses for producers. At the end of the season, all plants must be burned and all affected greenhouses, including the irrigation circuit, must be decontaminated.

International cooperation is crucial

-We are trying to protect agriculture from the virus-, says Denise Altenbach, explaining her battle against tomato brown rugose virus, which poses no risk to humans. -As with the flu and Covid-19, it isn-t always easy to tell a ToBRFV infection apart from an infection by other viruses based on symptoms alone. Only our molecular tests can clarify whether or not we are dealing with ToBRFV.- A further piece of the puzzle in controlling ToBRFV is international exchange, in which Agroscope takes part. In this way, Swiss experts can benefit from the experience of other countries that have already been grappling with ToBRFV for some time now.

Background information

Tomato Brown Rugose Fruit Virus (ToBRFV) was identified in Switzerland for the first time in 2021, on a tomato production farm in Thurgau canton. This plant disease attacks tomatoes and peppers, other host plants in the field or in the environment are currently not known. Yield losses of up to 100 per cent are possible. Highly contagious, ToBRFV survives for a long time on plant residues, in the soil and in greenhouses. As a quarantine organism, ToBRFV is a notifiable disease subject to compulsory control, and is monitored by the federal and cantonal plant protection services.