biology

Potato spindle tuber viroid

Potato spindle tuber viroid 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 Potato spindle tuber viroid rather than just read about it. In short: The potato spindle tuber viroid (PSTVd, Pospiviroid fusituberis) was the first viroid to be identified. PSTVd is a small, single stranded circular RNA molecule closely related to the chrysanthemum stunt viroid.

Key takeaways

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

Reference excerpt

The potato spindle tuber viroid (PSTVd, Pospiviroid fusituberis) was the first viroid to be identified. PSTVd is a small, single stranded circular RNA molecule closely related to the chrysanthemum stunt viroid. Present within the viroidal RNA is the Pospiviroid RY motif stem loop common to its genus. The natural hosts are potatoes (Solanum tuberosum) and tomatoes (Solanum lycopersicum). All potatoes and tomatoes are susceptible to PSTVd and there is no form of natural resistance. Natural infections have also been seen in avocados and infections in other solanaceous crops have been induced in the laboratory. Until 2017 PSTVd was thought to be unable to infect Solanum sisymbriifolium. Then in May seeds exported by a Dutch company were noticed to be infected. These seeds were shipped from the company, but had been originally bred to their specifications in two Asian countries. PSTVd also causes tomato bunchy top and is seed transmitted in tomato. It contains single stranded RNA without protein coat.

Discovery It was discovered in 1971 by Theodor Otto Diener, who was a plant pathologist at the U.S Department of Agriculture's Research Center in Beltsville, Maryland. He named it viroid because it is 1/80th the size of a virus.

Strains and their symptoms Different strains of PSTVd exist and symptoms range from mild to severe. Mild strains produce no obvious symptoms. Symptoms in severe strains are dependent on environmental conditions and are most severe in hot conditions. Symptoms may be mild in initial infections but become progressively worse in the following generations. Common symptoms of severe infections include color changes in the foliage, smaller leaves and spindle-like elongation. Sprouting also occurs at a slower rate than in unaffected potatoes. Infected tomatoes are slower to show symptoms which include stunted growth with a ‘bunchy top’ caused by shortened inter-nodes. Leaves become yellow or purple and often become curled and twisted. Necrosis eventually occurs in the veins of the bottom and middle leaves and the top leaves decrease in size. Fruit ripening is also affected leading to hard, small, dark green tomatoes. Long distance spread of PSTVd usually occurs via infected seeds but transmission via aphids (Myzus persicae) also occurs but only in the presence of PLRV (potato leaf roll virus). Mechanical transmission also occurs once it has been introduced to an area.

Primary and secondary structure of PSTVd PSTVd comprises 359 nucleotides. Used is the type genome V01465.

Course of infection Systemic movement within the infected host is through the phloem.

References

Ding, Biao (2009). "The Biology of Viroid-Host Interactions". Annual Review of Phytopathology. 47 (1). Annual Reviews: 105–131. doi:10.1146/annurev-phyto-080508-081927. ISSN 0066-4286. PMID 19400635.

Bibliography

Agrios, George N., 1936- Plant pathology (3rd edition) San Diego: Academic Press, 1988. Singh, R.P; Fletcher J.D.; "Background of disease (potato spindle tuber) and method of control", Agriculture and Agri food Canada, Crop & Food Research New Zealand Retrieved November 15, 2007 DEFRA Plant Health "Pathogen and plant damage (potato spindle tuber)" Retrieved November 15, 2007, from George N. Agrois, Plant Pathology (3rd Ed) San Diego: Academic Press,(1988).

Worked examples

Example 1 — a first encounter with Potato spindle tuber viroid

Start with the simplest possible case. Write down what Potato spindle tuber viroid 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 Potato spindle tuber viroid 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 Potato spindle tuber viroid 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 Potato spindle tuber viroid

In research: Potato spindle tuber viroid 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 Potato spindle tuber viroid 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: Potato spindle tuber viroid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Potato diseases, Tomato diseases, Viral plant pathogens and diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Potato spindle tuber viroid 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 Potato spindle tuber viroid in 20 minutes

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Close the page and write down what Potato spindle tuber viroid means in your own words.
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Work through the three examples above with pen and paper.
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Frequently asked questions

What is Potato spindle tuber viroid in simple terms?

Why does Potato spindle tuber viroid 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 Potato spindle tuber viroid?

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 Potato spindle tuber viroid.