Tobacco Mosaic & Cucumber Mosaic Viruses: Key Differences and Impact
The mosaic plant disease is an umbrella term for a group of virulent diseases that infect various types of foliage. The eponymous mosaic virus causes the condition. The mosaic viruses come from a range of unrelated lineages, and no taxon unites the group. The virus affects many economically significant crops such as tobacco, tomato, cucumber, beet, alfalfa, and so forth. The virus causes a mottled appearance in plants.
Plant viruses may be hard to detect as the symptoms are diverse and akin to nutrient deficiency or herbicide injury. But some of the common mosaic symptoms are –
The most typical sign of mosaic infection is yellow, white or green stripes, streaks or spots on the foliage.
The plant leaves may become wrinkled, curled or puckered.
There will also be visible yellowing of plant veins.
The yield capacity declines, and the plants suffer from stunted growth.
The fruits infected by the mosaic virus may appear mottled and have warty areas on the surface.
The mosaic symptoms may be masked or latent, mainly when the temperature is below 81 degrees Fahrenheit. Aphids and other insects, mites, fungi and nematodes spread the causal viruses. Like most viruses, the mosaic virus is also contagious, and pollen and seeds can transmit it via air. Often, soil, seed, starter pots and containers can also be infected by the virus, thereby passing it on to the plant. Cuttings or divisions from infected plants will also carry the virus to the new plant.
Tobacco Mosaic Disease
A viral infection of foliage, the tobacco mosaic disease, is a common viral disease that affects plants worldwide. The cause of the disease is the Tobacco Mosaic Virus, or TMV, which was the first plant virus to be ever identified. Irrespective of its name, the ‘tobacco’ mosaic virus can infect over 350 species of herbaceous and woody plants. The common hosts of the virus are tobacco, potatoes, tomatoes, cucumbers, and the like. The tobacco mosaic disease tremendously impacts vegetables wherein there is so much reduction of the yield and quality that commercial selling becomes impossible. The Tobacco Mosaic Virus survives in infected plants, their seeds, and the debris of infected plants. TMV can stay for long periods, and owing to its stability, the virus can survive on hands, clothing gardens, gardening tools, etc., and we can pick it from there. The tobacco mosaic disease is highly transmissible and is most typically spread by handling infected plants. Contagion via gardening tools is also pretty common.
The tobacco mosaic disease symptoms vary in type and severity, depending upon the plant species, plant age, variant of the infecting virus and likewise. But, some of the recurring signs that TVM infects a plant are
Blotchy and dark or light irregular patches on the leaves called leaf mosaic.
Curling, wrinkling and cupping of leaves
Stunted growth and dwarfism in the infected plant
The fruits of the infected plant are more diminutive and malformed with an off-putting taste.
Cucumber Mosaic Disease
Cucumber Mosaic Virus (CVM) virus causes disease among plants known as cucumber mosaic disease. CVM is one of the most common and destructive cucurbit viruses and prevalent throughout the temperate and tropical regions of the world. The virus can infect over 1200 plant species. The disease is highly infectious and can be transmitted from one plant to another plant, both mechanically by sap and by aphids. It can also be transmitted via seeds and parasitic weeds. If a plant is suffering from the cucumber mosaic disease, the typical yield losses range from 10 to 20 per cent, and even failures of up to 100 percent can occur.
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Tomato Mosaic Disease
The tomato mosaic disease is a highly contagious and severe condition infecting plants. The disease is brutal to identify as symptoms vary widely depending upon the plant's species and age, the strain of the infecting virus, environmental conditions, and so forth. Furthermore, it is challenging to distinguish the tomato mosaic disease from the closely related tobacco mosaic disease. You can identify the Tomato Mosaic Virus symptoms at all stages of growth, and the virus may infect any part of the plant.
Conclusion
Mosaic disease is an amalgamation of different virulent infections caused by mosaic viruses. Numerous strands of the mosaic virus lead to a range of mosaic diseases. The concept of plant mosaic disease may seem tedious, but with the proper preparation, the topic becomes relatively manageable. The optimal technique is to study the basics first, then move to particular types of mosaic infections such as the Tobacco Mosaic Virus, the Cucumber Mosaic Virus, etc. Moreover, complementing the preparation with past years’ question papers, concept pages, and educational videos goes a long way.
FAQs on Mosaic Disease: Causes, Symptoms, and Control
1. What exactly is mosaic disease in plants?
Mosaic disease refers to a set of symptoms caused by various plant viruses. These viruses interfere with a plant's natural development, particularly affecting the leaves, causing discolouration and poor growth. A classic example studied in biology is the Tobacco Mosaic Virus (TMV).
2. What are the common signs or symptoms of a mosaic virus infection?
The most recognisable symptom is a distinct mosaic-like pattern on the leaves, featuring patches of light green, yellow, and dark green. Other common signs that a plant is infected include:
- Stunted or unusually slow growth.
- Leaves that appear wrinkled, curled, or distorted.
- A noticeable yellowing of the leaf veins.
- Fruits or flowers that are misshapen or poorly developed.
3. How does mosaic disease spread from one plant to another?
Mosaic viruses typically spread in two main ways. The most common is through insect vectors, such as aphids, that carry the virus from an infected plant to a healthy one as they feed. It can also be transmitted mechanically through contaminated gardening tools, hands, or even when an infected leaf rubs against a healthy plant.
4. Can you give some examples of plants commonly affected by mosaic viruses?
Mosaic viruses can infect a very broad range of plants, impacting both agriculture and gardening. Some of the most frequently affected plants include tobacco, tomatoes, cucumbers, peppers, potatoes, and beans. Many ornamental flowers, like roses, can also be susceptible to certain strains of the virus.
5. How is mosaic disease in plants managed or treated?
Unfortunately, there is no cure for plants once they are infected with a mosaic virus. Because of this, management strategies focus entirely on prevention. The most effective methods include removing and destroying any infected plants immediately, controlling insect populations, using certified virus-free seeds, and regularly disinfecting all tools.
6. Why is this condition called 'mosaic' disease?
The name 'mosaic' is a direct description of the pattern the virus creates on a plant's leaves. The virus destroys the chloroplasts in some leaf cells, which stops them from producing the green pigment chlorophyll. This creates yellow or pale patches right next to healthy green areas, resulting in a pattern that looks like an artistic mosaic tile design.
7. Is the mosaic virus harmful to humans if we eat an infected fruit or vegetable?
No, plant viruses like the mosaic virus are not harmful to humans. These viruses are specific to plants and cannot replicate or cause illness in human cells. While an infected vegetable might look unappealing or taste slightly different, it is generally considered safe to eat. The main problem caused by the disease is the damage to the crop's health and yield.
8. What makes the Tobacco Mosaic Virus (TMV) so important in the history of biology?
Tobacco Mosaic Virus is historically significant because it was the very first virus to be discovered. In the late 1800s, scientists found that the agent causing disease in tobacco plants was smaller than any known bacteria. This led to the identification of a completely new type of pathogen, which was named a 'virus', and its discovery launched the entire scientific field of virology.
