Unknown planting material a risky business

Concerns have been raised over nurseries operating without proper accreditation, and the potential danger of unwittingly spreading disease by removing cuttings from infected vineyards. Prue Henschke discusses what this means for grapegrowers in Australia and what steps are being taken to reduce the risks.

 

The role of the vine improvement and vine nursery sector is significant to the grapegrowing industry. In 2017, 4.34 million cuttings were supplied to nurseries who in turn supplied customers in every Australian state.

Vine improvement’s primary goal is to supply high health status propagation material to the industry. Grapevine cultivars (varieties and their clones), known as ‘mother vines’, are held in three main collections across Australia with records of their origins, DNA testing and regular virus testing.

Source blocks are established in appropriate regions in commercial vineyards under agreement with the vineyard owner.

 

Each regional South Australian vine improvement group takes dormant cuttings from these blocks under Vine Industry Nursery Association (VINA) accreditation protocols to supply vine nurseries who should also be operating under accreditation protocols to provide high quality planting material to their customers.

 

However, not all nurseries operate under VINA accreditation, or alternative quality assurance accreditation schemes.

But this isn’t the only problem when it comes to planting material.

 

When growers or winemakers take a few cuttings from a vineyard down the road, they may potentially be spreading disease and limiting important traceback pathways in the event of a biosecurity incursion.

 

While we don’t know the extent of ‘vineyard next door’ propagation, we know it’s happening and we know it’s a major risk. The risk is amplified with unaccredited nurseries obtaining their cuttings from untested sources with no traceability back to a mother vine.

This risk may vary between wine grape, table grape and dried fruit industries, but any level of risk is a concern to the entire grapegrowing industry in Australia.

Up until this year, virus testing has involved the 13A test – Leaf Roll Virus 1 (LRV1) and Leaf Roll Virus 3 (LRV3) and GVA viruses are generally tested for annually in early winter depending on customer orders prior to cuttings being taken – and generally only material that tests negative is sold, depending on the customer.

 

The three main collections of mother vines are tested on a three-year cycle, with the full collection at Monash in South Australia, recently being tested with the A1 test which covers the 12 main viruses.

 

There are some viruses that should not be negotiable like LRV1 and LRV3, because of their ability to spread through insect vectors. New Zealand and South African vineyards have suffered badly from the spread of LRV3 in particular – a situation Australia does not want to experience.

The new test for Grapevine Pinot Gris Virus (GPGV) was introduced by Australian laboratories in 2015 and by quarantine facilities in 2014.

 

Reliability of sampling and testing is still uncertain; it appears from initial overseas research that green tissue testing in spring will most reliably show the presence of the virus.

 

This may also depend on what green tissue is sampled.

 

A sampling trial is underway to narrow down the most reliable time of sampling in Australia – autumn, winter or spring – and how the sampling is done.

 

Further work is planned to review relevant research published on GPGV from overseas, to assess the potential risk from GPGV in Australia and to highlight areas of future research required.

Following the GPGV incursion, the process of incursion management will also be considered, with the connections and communication between the grapevine propagation sector (vine improvement and vine nurseries), importation procedures and biosecurity reviewed.

A number of vine improvement associations carried out testing last spring for GPGV.

 

To optimise high health planting material, propagation material should be withdrawn from sale if it tests positive for GPGV.

 

It will be interesting to watch the progress on this as GPGV appears to have a varying impact on yield and vigour, depending on the variety.

 

Overseas research reports that Pinot Gris and Gewürztraminer are the most susceptible varieties.

 

Where GPGV is found in mother vines, they will be cleaned up by virus elimination methods.

 

These elimination methods are yet to be developed, thus it will take a number of years to eliminate GPGV from infected mother vines.

It shows how careful we need to be in importing grapevine material into Australia and how important it is to source the material from a high health status germplasm overseas.

 

We need to fully respect the role of non-propagation agreements as once they are broken the overseas providers can remove their material in Australia and also remove access to new cultivars.

 

We still do not know how GPGV came into Australia, in what variety/ies and even how long ago, given that a method of detection was only introduced in Australia in 2015.

As growers and winemakers, we need to smarten up our act with biosecurity.

This year, we encourage you when sourcing planting material to ask for proof of the virus status, for proof of identity from a DNA test and for proof of the nursery’s accreditation with VINA.

 

Keep that information as well as the clonal identity; it could prove to be very valuable in the future for traceability purposes.

With the interest in newly imported varieties and clones, these three questions are vital to stop the spread of any biosecurity threat.

Prue Henschke is VI and VINA representative to the National Vine Biosecurity Committee, chair of Adelaide Hills Vine Improvement Inc. and viticulturist at Henschke Cellars.

 

*This article was originally published in the Australian and New Zealand Grapegrower & Winemaker May edition.

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