Unbeknownst to many, Hungary has a rich history of wine growing. Traditions that date far beyond the Roman Empire and for a time stunted by communism and publicization of vineyards. This, to the detriment of wine quality in Hungary saw previously popular good quality brands that had the same if not more notoriety as French wines deteriorate into oblivion (Tokaji being a prime example). Fortunately since the fall of Communism in 1990 quality has come back.
However, high loses caused by plaguing pathogens continuously threaten the yields, mortality and quality of stocks. It was only a little over fifty years ago that Dr. János Lehoczky and his colleagues at the Research Institute for Viticulture, in Kecskemét, that a certification scheme for producing virus free nursery materials was introduced.
Grapevine certification programs ensure nursery growers have tested and pathogen free vine-lings. This in turn saves growers millions of dollars and ensures that they have the right protection against them and thus guaranteeing vine longevity and wine quality.
Unique Hungarian Diseases
Their report, albeit mostly untranslated since it is in Hungarian, points to Grapevine Fleck Virus (GFkV) and Grapevine leafroll-associated virus (GLRaV) as playing a leading role in the degradation of local grapevines. Since then, there have been numerous studies and diagnostical methods employed into the research of producing virus-free propagating material. Technology continues to play an important role in identifying new diseases.
One can simply look at the devastation caused by the Phylloxera virus to see just how important this is. Cautioned by a dark history that saw the entire wine world at its knees.
One should note that while many of the diseases that affect vines can be spotted easily on the vine, such as red leaf, they can go unnoticed during vine dormancy when growers cut the wood for propagation. Other viruses or disease-causing agents may be so low that they are either virtually unrecognizable or that the variety itself is tolerant. New diseases are discovered each year as mutations happen, others can simply be acquired through importing infected stock.
Primary Testing Methods
While testing methods are many, the following three can be highlighted;
- Direct Culture (inoculating indicator Plants);
This, the oldest form of Lab testing is not only commonly used, but useful in identifying bacterial and fungal diseases. An infected tissue sample is placed into a selective culture media and observed for what grows out of it. In grapes bacteria like Pierce’s disease and Crown Gal as well as fungal ones like; Oak root Fungus (armillaria), Eutypa, Crown Rot (Phytophthora), Botrytis and Phomopsis can be detected.
- Serolical Tests;
Something akin to vaccination. Serological tests involve injecting an animal with a purified version of the virus to create an antiserum. Antibodies that react to it are then purified and the resulting antiserum tested for effectiveness. The Enzyme-Linked Immunosorbent Assay (ELISA) test is most common but can only be successful if the samples are in good condition, from the appropriate tissue and produced at the right time of the year.
- Woody indexing. This involves grafting ‘clean’ buds onto stems that display symptoms. with Biological Indicators
Grape Vine Viruses
• Grapevine vein mosaic
Discovered in 1966. Grapevine Vein Mosaic produces a vein banding appearing as a pale green mosaic on the main veins of the leaf. The disease can be spread by vegetative propagation and grafting. Gloire de Montpellier is used as indicator variety.
• Grapevine vein necrosis
Reported in 1986, its symptoms are dead cell tissues of the vein-lets underside of the leaf blade. This develops from the base of the shoot and as it grows, on the young leaves. It can develop into tendrils and result in green shoots dying. Its cause is unknown and so is its host plant. Care is to be taken while grafting as this causes it to spread.
• Grapevine fanleaf virus (GFLV)
First recorded by Sárospataki in 1964 (Hungary). Its many strains cause varying symptoms and severity. It infects all cultivars and can cause a slow decline or a swift destruction of an entire crop. Symptoms range from abnormal bunching. Leaf deformations, fan-shaped primary veins and infected vines. Sight of yellow mosaic, vein banding and enlarged petiolar sinus are also indicators of the virus.
While these are a few of the types of disease-causing organisms to watch out for, new methods are employed daily to ensure the integrity of the vines. One More recently developed is Molecular indexing; the target the plant pathogen’s genetic genome. Methods such as PRC selectively amplify small parts of the pathogen’s genome and prove to be effective since each has its own unique genetic identifier.