CMV AND ToMV

• Viruses are microscopic infectious agents consisting of genetic material (DNA or RNA) enclosed within a capsid protein coat. They are considered obligate intracellular parasites because they cannot replicate or carry out metabolic processes outside a host cell.
• Viruses cannot reproduce independently and instead rely on infecting living cells of organisms, such as plants, animals, or microorganisms, to replicate and produce new viral particles.
• They hijack the cellular machinery of the host cell to replicate their genetic material, assemble new virus particles, and spread to other cells or hosts.
• Viruses can infect all forms of life, including animals, plants, bacteria, fungi, and even other viruses.
• They cause a wide range of diseases, including common colds, influenza, measles, HIV/AIDS, COVID-19, and many others. Viruses can also impact agricultural productivity by causing diseases in crops and livestock.
• Due to their simplicity and dependence on host cells, viruses are often regarded as biological entities that exist on the boundary between living and non-living things. They are highly diverse and can exhibit a variety of shapes, sizes, and genetic compositions.

3. About CMV and ToMV

• ToMV (Tomato mosaic virus) and CMV (Cucumber mosaic virus) are two plant pathogens that cause similar damage to crops.
• ToMV belongs to the Virgaviridae family and is closely related to the tobacco mosaic virus (TMV), while CMV has a larger host pool and was first identified in cucumber in 1934.
• ToMV primarily spreads through infected seeds, saplings, agricultural tools, and human touch, whereas CMV is primarily spread by aphids, although human transmission is also possible but rare.
• Conditions of high temperature and intermittent rain favor the spread of CMV by promoting aphid multiplication.
• In Maharashtra, farmers have blamed seed manufacturers and nurseries for the spread of ToMV, emphasizing the importance of maintaining bio-safety and implementing seed treatment at nurseries to prevent future virus spread.

Image Source: The Indian Express

4. Symptoms

• Both ToMV and CMV can result in nearly 100% crop loss if not treated promptly.
• ToMV-infected plants exhibit alternating yellowish and dark green areas on the foliage, often appearing as blisters. Leaf distortion, twisting, and necrotic spots on the fruit leading to overripening are common symptoms. Young plants are stunted, and fruit setting is impacted.
• CMV also causes leaf distortion but typically affects leaves at the top and bottom while leaving the middle relatively unaffected. In cucumber, CMV causes a mosaic-like pattern of yellow and green spots. In tomatoes, fruit formation is hindered, resulting in distorted and small fruit.
• In general, CMV causes stunting and reduced crop production, with specific effects varying depending on the host plant.

5. Prevention and Control of the Virus

• Dr. Reddy emphasizes the importance of adhering to biosafety standards in nurseries and implementing compulsory seed treatment to prevent the spread of ToMV.
• Farmers purchasing trays of saplings should carefully inspect them before planting and discard any visibly infected material.
• Vigilance for signs of infection throughout the cropping cycle is crucial, and infected plants should be promptly removed without allowing contact with healthy plants.
• ToMV can remain dormant in weeds and plant residues, so thorough clearing of fields from weeds and plant material is necessary before fresh planting.
• ToMV cannot be cured, but its infection can be controlled through good agricultural practices.
• Reports of ToMV are now emerging from various states beyond Maharashtra, including Karnataka and Andhra Pradesh.
• Controlling CMV is challenging due to its wide range of host plants. The most effective approach is to control aphids, which can be achieved by spraying quick-acting insecticides or mineral oils on plants.
• Care must be taken not to disturb aphids, as it can lead to the spread of the virus to other fields.
• Monitoring aphid migration is essential to implement preventive measures during crop planting.

For Prelims: ToMV (Tomato mosaic virus), CMV (Cucumber mosaic virus), DNA, RNA, Viruses, Replication, Aphid, Leaf Distortion. For Mains: 1. Discuss the control and prevention strategies for two plant viruses, Tomato mosaic virus (ToMV) and Cucumber mosaic virus (CMV). (250 Words)

 

Previous year Question   1. Which of the following statements is/are correct? (UPSC 2013) 1. Viruses lack enzymes necessary for the generation of energy. 2. Viruses can be cultured in any synthetic medium. 3. Viruses are transmitted from one organism to another by biological vectors only. Select the correct answer using the codes given below. A. 1 only B. 2 and 3 only C. 1 and 3 only D. 1, 2 and 3 Answer: A   2. Viruses can infect (UPSC 2016) 1. Bacteria 2. Fungi 3. Plants Select the correct answer using the code given below. A. 1 and 2 only B. 3 only C. 1 and 3 only D. 1, 2 and 3 Answer: D   3. Consider the following statements : (UPSC 2021) 1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes. 2. Common cold is sometimes caused by an adenovirus whereas AIDS is caused by a retrovirus. Which of the statements given above is/are correct? A. 1 only B. 2 only C. Both 1 and 2 D. Neither 1 nor 2 Answer: B

 

Source: The Indian Express