CMV AND TOMV VIRUS
WHY IN NEWS ?
- Tomato farmers in Maharashtra and Karnataka have blamed two different viruses for the loss of yields earlier this year.
MORE ABOUT THE NEWS :
- Farmers in Maharashtra have said their tomato crop was impacted by attacks of the cucumber mosaic virus (CMV).
- Farmers in Karnataka and other South Indian states have blamed the tomato mosaic virus (ToMV) for 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.
ABOUT CMV AND TOMV VIRUS:
- The two plant pathogens have similar names and cause similar damage to crops, but they belong to different viral families, and spread differently.
- ToMV belongs to the Virgaviridae family and is closely related to the tobacco mosaic virus (TMV).
- ToMV hosts include tomato, tobacco, peppers, and certain ornamental plants.
- CMV has a much larger host pool that includes cucumber, melon, eggplant, tomato, carrot, lettuce, celery, cucurbits (members of the gourd family, including squash, pumpkin, zucchini, some gourds, etc.), and some ornamentals.
- CMV was identified in cucumber in 1934, which gave the virus its name.
- CMV causes a systemic infection in most host plants, but may remain symptomless in some crops like alfalfa.
- Symptoms of cucumber mosaic can vary greatly depending on the crop infected and the age of the plant when infection occurs.
HOW DO THESE VIRUSES SPREAD ?
- ToMV spreads mainly through infected seeds, saplings, agricultural tools and often, through the hands of nursery workers who have failed to sanitise themselves properly before entering the fields.
- It would require only a few infected saplings for the virus to take over an entire field in a matter of days.
- CMV is spread by aphids, which are sap-sucking insects.
- CMV too can spread through human touch, but the chances of that are extremely low.
- Conditions of high temperature followed by intermittent rain, which allow aphids to multiply, are conducive to the spread of CMV.
- These conditions were seen in Maharashtra — the late rabi crop (planted in January-February) faced a sudden bout of rain followed by extreme heat.
EFFECT OF VIRUS ON CROPS:
- Both viruses can cause almost 100 per cent crop loss unless properly treated on time.
- The foliage of plants infected with ToMV shows alternating yellowish and dark green areas, which often appear as blisters on the leaves.
- Distortion of leaves and twisting of younger leaves are also symptoms.
- The fruit develops necrotic spots, which leads to overripening.
- Younger plants are dwarfed, and fruit setting is affected.
- CMV too causes distortion of leaves, but the pattern is different.
- Often leaves at the top and bottom are distorted while those in the middle remain relatively blemish-free.
- In cucumber, the virus causes a mosaic-like pattern of alternating yellow and green spots.
- In tomato, fruit formation is affected, and in some cases the fruit is distorted and small.
HOW TO SAVE CROP FROM THESE VIRUSES ?
- As farmers in Maharashtra have blamed seed manufacturers and nurseries, it is very important to ensure that nurseries maintain bio safety, and restrict entry into the premises.
- Seed treatment at the nursery is necessary to prevent future spread of the virus.
- Farmers who buy trays of saplings should check before planting, and discard any visible infected material.
- They should also look out for signs of infection throughout the cropping cycle, and remove infected plants without allowing it to touch healthy ones.
- Plants cannot be cured of ToMV, but the infection can be controlled with good agricultural practices.
- An eye must be kept on aphid migration so that measures can be taken while planting the crop.
- Taking the issue of food safety in consideration, controlling CMV is more difficult, given the large number of hosts the virus can live on.
- The best way is to stop the aphids, which can be done by spraying quick acting insecticides or mineral oils on the plants.
SYLLABUS: MAINS, GS-3, AGRICULTURE
SOURCE: INDIAN EXPRESS