The impact of grapevine virus diseases on the local wine industry is increasing alarmingly.
It is especially grapevine leafroll disease that has the wine community worried and that has become the primary target for South African researchers. Mounting concerns from industry have prompted Winetech to reorganise local grapevine virus research in a single virus programme under the leadership of Dr Johan Burger of the University of Stellenbosch.
During the last two decades, grapevine viruses have grown in stature – from being considered as semi-living organisms of uncertain pathological status to being recognised today as causing some of the most important diseases (in the case of grapevine leafroll disease) affecting the vineyards of the Western Cape. One of the most worrying aspects of this disease is its rapid rate of spread, better known as “the re-infection problem”. It is estimated that a newly established vineyard can become completely infected (80% plus) in 5 to 6 years. These levels of infection have detrimental influences on both fruit quality and yield, and contribute significantly to the relatively short lifespan of our vineyards.
Several research projects to counter virus diseases have been initiated over the years, but these did not make any significant progress towards solving the problem. Winetech recently made a strategic decision to reorganise the virus research projects that it supports, in a single virus programme. Although most existing research projects will continue, it was decided that the research effort should be directed at a few focus areas. Projects submitted for future funding will also be accommodated in one of these areas. The focus areas are:
- Eradication, which includes projects to determine the current status of leafroll disease, the re-infection problem, as well as the elimination of viral vectors.
- Etiology, which includes projects to elucidate the different viral pathogens contributing to the disease complexes.
- Resistance, includes different approaches to introduce viral resistance into grapevine.
- Supporting technologies, encompass several projects to develop technologies needed in many of the other areas, such as genetic transformation of grapevine, greenhouse and field trials, and the maintenance of a reliable virus garden.
We believe these focus areas address all relevant research aspects of the virus problem. It includes projects that should yield results in the short to medium term, like preventative measures to curb virus spread, as well as longer term efforts to introduce virus resistance by genetic engineering. There is also a good balance between market-driven research such as virus resistance and more fundamental projects, like elucidating the etiology of Shiraz disease. Table 1 contains a complete list of current projects.
The programme is co-ordinated by the newly formed grapevine virus advisory committee, consisting of Messrs E G le Roux (Distell, chair), J H Booysen (Winetech), G le R Kriel (KWV), Prof I S Pretorius (US), Drs E F Beukman (VIA), I Trautmann (ARC) and J T Burger (US). This committee will determine current and future research priorities and make recommendations to Winetech regarding progress with existing projects. Annual progress reports, as well as new applications for funding, will be evaluated by a grapevine virus research committee consisting of Dr J T Burger (US, chair), G Pietersen (ARC), M A Vivier (US), I Trautmann (ARC), Profs F C Botha (US), E P Rybicki (UCT) en D Gonsalves (Cornell University).
In order to provide the above committees with a picture of the current status of grapevine virus research in South Africa, and to establish an electronic database of research activities, a questionnaire was distributed among all researchers, who are currently receiving research support from Winetech, as well as new applicants that were granted funding from 2001 onwards. Results from the questionnaires indicated that two centres of expertise in grapevine virus research exist in South Africa. At the ARC Plant Protection Research Institute in Pretoria a critical mass of researchers reside, with the expertise and excellent facilities to do virus surveys and diagnostics (EM, serological, and molecular), to produce both monoclonal and polyclonal antibodies, to do vector studies and to do etiological work. They also have the services of an electron microscopy (EM) unit. Although this group has the disadvantage of being located in Pretoria, they do link with their sister institute, ARC Infruitec-Nietvoorbij in Stellenbosch, where more entomology and general virology expertise resides.
Another important research grouping is located at the University of Stellenbosch, and consist of researchers at the Institute for Wine Biotechnology (IWBT), the Department of Oenology and Viticulture and the Department of Genetics. The IWBT/Oenology and Viticulture group is the only one that can reliably transform grapevine in South Africa. This ability is essential for the introduction of virus resistance into grape cultivars. This group has excellent plant tissue culture facilities to do both transformation and regeneration, but is lacking a suitable transgenic glasshouse for evaluation of transformed plants. The Genetics Department concentrates on molecular virology. They are equipped to design and construct plant expression vectors for viral resistance, and work in close collaboration with the IWBT.
With some exceptions, progress with individual projects over the last year, has been good. We believe the previous lack of proper co-ordination and collaboration will be eliminated with the establishment of a single virus programme, with its defined focus areas. It is also foreseen that the annual evaluation system by the grapevine virus research committee will be more stringent and hence promote outcome-based research. The advisory committee has identified grapevine leafroll disease as the top research priority and is determined to see its researchers make good progress in finding a lasting solution to this disease. The status of virus diseases is, like most other issues in the wine industry, very dynamic. The grapevine virus advisory committee therefore invites commentary and suggestions from any stakeholders in the wine industry. The author can be contacted at the above address.