CMV AND TOMV - AGRICULTURE
News: CMV
and ToMV: The two ‘mosaic’ viruses that hit tomato crop in Maharashtra and
Karnataka
What's in the news?
● Tomato growers in
Maharashtra and Karnataka have blamed two
different viruses for the loss of yields earlier this year.
Key takeaways:
● Farmers
in Maharashtra have said their tomato crop was impacted by attacks of the
cucumber mosaic virus (CMV), while growers in Karnataka and other South Indian
states have blamed the tomato mosaic virus (ToMV) for crop losses.
CMV and ToMV:
● The
two plant pathogens have similar names and cause similar damage to crops, but
they belong to different viral families, and spread differently.
Tomato Mosaic Virus (ToMV):
● ToMV
belongs to the Virgaviridae family
and is closely related to the tobacco mosaic virus (TMV).
Host:
● ToMV
hosts include tomato, tobacco, peppers,
and certain ornamental plants.
Spread:
● ToMV
spreads mainly through infected seeds,
saplings, agricultural tools and often, through the hands of nursery
workers who have failed to sanitize 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.
Cucumber Mosaic Virus (CMV):
● CMV
was identified in cucumber in 1934, which gave the virus its name.
Host:
● 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.
Spread:
● 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.
Impacts of ToMV and CMV:
Both
viruses can cause almost 100 percent
crop loss unless properly treated on time.
ToMV:
● 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:
● 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.
● While
specific effects vary depending on the host, overall, CMV causes stunting and
lower production.
Control Measures:
● Following
biosafety standards in nurseries.
● Compulsory
seed treatment to stop the spread of
ToMV.
● Fields
must be cleared of weeds and plant
material before fresh planting.
● Plants
cannot be cured of ToMV, but the infection can be controlled with good agricultural practices.
● Spraying
quick acting insecticides or mineral oils
on the plants to control aphids.