A comprehensive review of Grapevine Pinot gris virus (GPGV), a virus first detected in Australia in 2016, has just been completed and will improve Australia’s knowledge base.
Following the review, a number of clear research areas have been identified, to assist the industry with its transition to effective management of GPGV.
One area of focus for the review was to recommend management strategies that could be implemented straight away across the viticulture supply chain, to reduce GPGV spread in Australia, based on available overseas research and limited Australian research conducted as part of the review.
As the virus is transmitted by vegetative propagation and grafting, starting with clean, high-health planting material is key. In addition, bud and blister mites (Colomerus vitis) are considered potential vectors of GPGV, contributing to vine-to-vine spread of the virus; therefore, a focus on vector control is important.
Particular to GPGV, infected varieties may show grapevine leaf mottling and deformation symptoms (deemed ‘sensitive’ varieties) or can appear seemingly healthy. Importantly, this means that GPGV may be spread from symptomless varieties to sensitive varieties.
Symptom expression has been reported overseas to vary between strains of GPGV, grape varieties, environments and growing seasons and therefore is not a definitive indicator of GPGV infection. Commonly reported symptoms such as delayed budburst, stunted shoots, chlorotic mosaic or mottled leaves which are sometimes distorted, might also be associated with other causes such as bud mites, fungi, nutritional or management issues, or environmental impacts. Laboratory testing is therefore the only definitive means of determining infection.
Key current management strategies for the germplasm, nursery and vine improvement sector include:
- Diagnostic testing of nucleus collections, mothervines and source blocks for GPGV.
- Diagnostic testing of grafted and own-rooted planting material for GPGV, pre-sale.
- Consider use of grapevine tissue culture and/or insect proof screening to hold high-health germplasm.
- Monitoring for visual symptoms, but noting that diagnostic testing is required to confirm GPGV presence.
- Active control of bud and blister mites.
- Use of virus removal treatments to produce virus-free propagation material.
- Removal of GPGV-infected vines.
Key current management strategies for grapegrowers include:
- Requesting evidence of GPGV testing on any purchased rootstock, wine or table grape variety for planting, replanting, grafting or vine replacement purposes.
- Monitoring for visual symptoms, but noting that diagnostic testing is required to confirm GPGV presence.
- Considered removal of infected vines.
- Active control of bud and blister mites.
“This review is just the first step in building our knowledge base about the virus in Australia,” said Suzanne McLoughlin, Technical Manager of Vinehealth Australia.
“It provided an excellent opportunity to determine what we know and what we don’t know about GPGV based on overseas research and limited studies in Australia. A number of key research areas were identified in this review which, if prioritised amongst other biosecurity needs, would greatly assist in Australia’s transition to management of GPGV.”
Key research areas identified by the review are to:
- Undertake a field survey to quantify incidence and distribution of GPGV – both in vines showing symptoms and vines without symptoms in Australia, including range of symptoms expressed, varietal sensitivity, agronomic impacts and strains of the virus present;
- Quantify varietal response to GPGV infection when it occurs on its own, compared to when it occurs in the presence of other viruses;
- Ensure that all Australian laboratories undertaking diagnostic testing for GPGV are using tests that will detect all the strains present in Australia;
- Conduct a large sampling trial over several seasons, with multiple table and wine grape varieties to confirming the most reliable time to conduct GPGV testing;
- Better understand the Australian vectors of GPGV and their management;
- Identify alternative hosts of GPGV in Australia and their role in GPGV spread; and
- Evaluate effective virus removal strategies.
The GPGV review was led by Vinehealth Australia, funded by Wine Australia, Vine Industry Nursery Association, Australian Grapevine Foundation Planting Service (now to be known as South Australian Vine Improvement Association) and a number of vine improvement associations, and authored by Fiona Constable, Agriculture Victoria Research, Libby Tassie, Tassie Viticultural Consulting and Suzanne McLoughlin, Vinehealth Australia.
For more information:
Click here to read the GPGV article that appeared in Wine Australia RD&E News February 2019 issue.
Click here to read the GPGV fact sheet produced as part of this review.
And watch out for a GPGV article in the March issue of Australian & New Zealand Grapegrower & Winemaker Magazine that provides further detail about the review.