Faster grape virus detection

The problem stems from a variety of factors, including slow testing methods, outdated policies, and the realities of growing wine grapes in North America.

Employing the same tools used to detect variants in COVID-19, however, could significantly reduce the burden viruses place on grape growers.

The current reality

In Canada and the United States, wine grape growers generally graft European grape varieties onto North American rootstocks in order to prevent a variety of diseases (mainly fungal), which can rapidly kill the vine. The solution does not help prevent the slow degradation and death caused by viruses, however, since the latter are transmitted between plants via insects.

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Grapevine red blotch virus on Cabernet Franc varietal in a Canadian vineyard. – Photo: Sudarsana Poojari

According to Sudarsana Poojari, senior scientist with Brock University’s Cool Climate Oenology and Viticulture Institute, all grape vine materials in Canada are imported from Europe and the United States. The Canadian Food Inspection Agency (CFIA) – the country’s federal food safety ministry – tests samples of these imports for a number of viruses.

“We import close to six million vines every year,” says Poojari. “I don’t think CFIA can look at even one per cent because of [practicality] barriers.” Even if vines could be checked en masse, the viruses the agency looks for are not necessarily the ones costing the wine industry money.

“By mandate CFIA doesn’t need to do anything if they find one,” Poojari says, listing red blot disease as a prime example. He adds European suppliers do not help the situation as they similarly don’t check their stocks for such pathogens.

Overall, Canadian growers are very limited when it comes to determining the quality of the vines they receive.

Testing more viruses quicker

In October 2020, Poojari and his colleagues at Brock University announced a partnership with the Canadian Grapevine Certification Network and others to fast-track the use of “High-Throughput Sequencing technology” as an alternative to conventional virus-testing in the country’s wine industry.

The technology allows analysts to quickly and efficiently sequence DNA and RNA, and is currently being used to identify and track variants of the COVID-19 virus.

When applied to grapes, this single genomic-based test would replace more than 30 tests currently being performed on grapevines to look for diseases, and speed up the release of virus-free grapevine material from three years to one year or less. Growers would thus have much earlier access to valuable new varieties.

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Virus free vines in the Brock University phytotron facility. – Photo: Sudarsana Poojari

A universal passport

As Poojari describes, the implementation of such a test – an action being pursued under a project called CLEan plAnt extractioN SEquencing Diagnostics (CLEANSED) – would allow grape growers to rapidly improve the health of their vineyards and boost the domestic capacity in the supply of much needed virus-free grapevine plant material.

“To get a one or two metre plant you need to wait two years…Currently it takes seven years to get into the hands of growers. We want to reduce this by three years,” he says. “What we are trying to reduce is the time for testing. This particular test can speed up the virus free certification from three to one year or less.”

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Sudarsana Poojari, Brock University. – Photo: Sudarsana Poojari

Additionally, Poojari says such a rapid testing system would also facilitate the movement of varietal clones between regions. It could, in effect, act as a universal passport for shipping between provinces, and potentially between countries.

All this is provided there is enough uptake by industry and the regulatory agencies involved – but in Canada, at least, this does not appear to be an issue. Indeed, the initiative has the backing and participation of a number of different partners, including propagators, growers, as well as aforementioned groups and others.

The genomic tool is currently on offer for those in the Canadian Grapevine Certification Network. Under the CLEANSED project specifically, Poojari and his colleagues plan to fine tune the method in an effort to make it more cost-effective for what he calls “large scale diagnostic operations.”

“We are currently offering HTS method for CGCN for domestic certification purposes, but with CLEANSED project we would fine-tune the existing HTS method to make it more cost-effective and for large-scale diagnostic applications. We intend to do this in the coming three years, which is the duration of the project,” he says.

Further information about the grape vine testing initiative, and the process itself, is available through the University’s website.