biology

Grapevine red blotch disease

Grapevine red blotch disease is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Grapevine red blotch disease rather than just read about it. In short: Grapevine red blotch disease (GRBD), also known simply as red blotch, is a viral disease of grapevine. The disease is caused by a single-stranded circular DNA virus, the species Grapevine red blotch virus, also known as Grapevine red blotch-associated virus, GRBaV.

Key takeaways

Grapevine red blotch disease belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Grapevine red blotch disease to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Grapevine red blotch disease from memory before moving on to harder problems.

Reference excerpt

Grapevine red blotch disease (GRBD), also known simply as red blotch, is a viral disease of grapevine. The disease is caused by a single-stranded circular DNA virus, the species Grapevine red blotch virus, also known as Grapevine red blotch-associated virus, GRBaV. First identified in California, the disease affects grapevines of all varieties and is internationally present. Symptoms typically include red blotches on the leaves of red varieties and in pale green or pale yellow blotches on white varieties. It significantly reduces the value of juice collected from the berries of affected vines, costing vineyard owners as much as $65,000 per acre. The discovery of red blotch and GRBaV is jointly credited to Mysore Sudarshana, a USDA-ARS virologist stationed at UC Davis, and Keith Perry and Marc Fuchs, virologists from Cornell. The three-cornered alfalfa treehopper (Spissistilus festinus) was confirmed as a vector for the disease in 2016, but there are currently no advised treatments for red blotch other than removing and replacing affected vines.

Discovery In 2008, UC Davis researchers Jim Wolpert and Mike Anderson suspected a new strain of grapevine leafroll disease had emerged at an experimental research station in Oakville, California. Mysore Sudarshana discovered the disease was entirely different and named it red blotch. After four years of research, he confirmed the disease was caused by GRBaV through a metagenomics approach by next-generation sequencing. Sudarshana also confirmed the virus affected many different varieties of grapevine through testing of Cabernet Sauvignon, Cabernet Franc, and Zinfandel. Concurrently, Keith Perry and Marc Fuchs encountered the same virus while DNA-testing a Cabernet Franc vineyard in New York. Unaware the virus affected many types of grapevines, they initially called the virus "grapevine cabernet franc–associated virus". In Spring 2011, Perry and Fuchs sent the DNA they had found to Sudarshana, who confirmed the virus was GRBaV. In Fall 2012, Sudarshana, Perry, and Fuchs formally presented grapevine red blotch disease as a joint discovery to the International Council for the Study of Viruses and Virus-like Diseases of the Grapevine.

Symptoms Red blotch presents with both foliar and fruit symptoms. Foliar symptoms typically begin appearing in mid-summer as irregular blotches on leaf blades at the base of infected grapevines. Over time, the blotches spread upward from the base to the top of the grapevine canopy. In red grape varieties, the blotches are red; in white grape varieties, the blotches may be pale green to pale yellow. Red blotch disease results in delayed berry ripening, altered berry color, and a smaller berry size. It adversely affects pH, anthocyanin levels, tannin levels, and other phenolic factors that reduce the quality and market value of wine made from affected grapes. Sugar accumulation may be significantly reduced, typically dropping by 3 degrees Brix and dropping by as much as 6 degrees Brix in some varieties. Premium wine producers in California estimate that a 100% red blotch infection can reduce the value of a vineyard by as much as $68,000 per acre. Research indicates that red blotch is not a new disease, but has been overlooked until its discovery at UC Davis in 2008 because its symptoms appear similar to those of grapevine leafroll disease. There are two key symptomatic differences between the diseases. While both diseases result in abnormal red coloring on affected grapevine leaves, leafroll affected leaves only turn red in and around the secondary veins of the grapevine leaf; red blotch affected leaves turn red in both the primary and secondary veins as well as in the interveinal zones. Secondly, unlike with leafroll, leaves affected by red blotch do not typically roll inwards at their edges. Symptoms of red blotch may also be mistaken for plant stress or nutritional deficiencies.

Cause Red blotch is caused by Grapevine red blotch virus, also called grapevine red blotch-associated virus (GRBaV), a single-stranded circular DNA virus. GRBaV is a member of the genus Grablovirus, and is one of only a few geminiviruses currently known to infect woody perennial plants. Within GRBaV, two groups of genetic variants have been identified so far.

Epidemiology Research suggests a wide geographic distribution, as well as a widespread occurrence in red and white vinifera cultivars. Infected vines have been identified in California, New York, Virginia, Maryland, Pennsylvania, Texas, and Washington. A nearly identical virus was found in Canada. GRBaV has been found both in young and mature vineyards, and has been detected in Cabernet Franc, Cabernet Sauvignon, Chardonnay, Malbec, Merlot, Mourvèdre, Petite Syrah, Petit Verdot, Pinot noir, Riesling, and Zinfandel.

Vectors In 2016, Sudarshana, UC Davis entomology professor Frank Zalom, and UC Davis post-doctoral researcher Brian Bahder identified the first known insect vector for GRBaV: the three-cornered alfalfa treehopper (Spissistilus festinus). Previously considered a minor vineyard pest in the North Coast, the three-cornered alfalfa treehopper spreads GRBaV while injecting salivary fluid into plant material to pre-digest it. The injection leads to tell-tale girdling at the injection site on grapevine petioles. The three-cornered alfalfa treehopper's preferred hosts include grasses, legumes, and its namesake alfalfa. These plants are often found on the edges of vineyards in riparian areas, which may explain the spread of the disease in some vineyards. Sudarshana and Zalom are currently investigating closely related insect species to identify additional vectors. GRBaV is transmittable by grafting, but there is no evidence that it can be transmitted by mechanical means such as pruning shears or other gardening tools.

Management Currently, the only advised method of control is replacing infected vines with new, virus-free grapevines, which results in years of lost production until the new vines mature. Economic analyses suggest replacing individual symptomatic vines if red blotch is present in less than 30% of a vineyard, and replacing the entire vineyard if red blotch is present in more than 30%. The use of pesticides to control the three-cornered alfalfa treehopper is not currently recommended.

References

Worked examples

Example 1 — a first encounter with Grapevine red blotch disease

Start with the simplest possible case. Write down what Grapevine red blotch disease claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Grapevine red blotch disease before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Grapevine red blotch disease ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Grapevine red blotch disease

In research: Grapevine red blotch disease appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Grapevine red blotch disease in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Grapevine red blotch disease is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geminiviridae, Viral grape diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Grapevine red blotch disease outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Grapevine red blotch disease in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Grapevine red blotch disease means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Grapevine red blotch disease out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Grapevine red blotch disease in simple terms?

Why does Grapevine red blotch disease matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Grapevine red blotch disease?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Grapevine red blotch disease.