CMV and ToMV Virus | 07 Jul 2023

Why in News?

Tomato growers in Maharashtra attribute crop decline to the Cucumber Mosaic Virus (CMV), while growers in Karnataka and other South Indian states blame the Tomato Mosaic Virus (ToMV) for their crop losses.

• Over the last three years, growers of tomato have complained of increased infestation with these two viruses, leading to partial to complete crop losses.

What are ToMV and CMV?

• ToMV:
  • About:
    • ToMV belongs to the Virgaviridae family and is closely related to the Tobacco Mosaic Virus (TMV). It infects tomato, tobacco, peppers, and certain ornamental plants.
    • It was first identified in tomato in 1935.
  • Transmission:
    • ToMV mainly spreads through infected seeds, saplings, agricultural tools, and human contact.
    • It can also be transmitted by some insect vectors, such as thrips and whiteflies.
  • Effects on Crops:
    • ToMV causes green mottling and yellowing of leaves, which often appear as blisters or fern-like patterns.
    • The leaves may also curl downwards or upwards and become distorted.
    • Younger plants are dwarfed, and fruit setting is affected.
  • Control Measures:
    • Emphasize biosafety standards in nurseries and implementing compulsory seed treatment.
    • Farmers should inspect saplings before planting and discard any infected material.
• CMV:
  • About:
    • CMV belongs to the Bromoviridae family and is one of the most widespread plant viruses. It has a broader host range, affecting cucumber, melon, eggplant, tomato, carrot, lettuce, celery, cucurbits, and some ornamentals.
    • It was first identified in cucumber in 1934.
  • Transmission:
    • CMV mainly spreads through aphids, which are sap-sucking insects that can acquire and transmit the virus within minutes.
      • It can also be transmitted by seeds, mechanical inoculation, and grafting.
  • Effect on Crops:
    • Distorts leaves, primarily at the top and bottom while leaving the middle relatively unaffected.
    • In cucumber, it causes a mosaic-like pattern of yellow and green spots.
    • Affects fruit formation and leads to stunting and reduced production.
  • Control Measures:
    • Focus on preventing aphids by using quick-acting insecticides or mineral oils.
    • Care should be taken to avoid aphid migration and spread of the virus to other fields.
• Similarity:
  • Both viruses have a single-stranded RNA genome that is encapsidated in a rod-shaped protein coat. Both viruses enter the plant cells through wounds or natural openings and replicate in the cytoplasm.
    • They then move systemically throughout the plant via the phloem.
  • Also, Both viruses can cause almost 100% crop loss unless properly treated on time.

Source: IE