TMV has a very wide host range and has different effects depending
on the host being infected. It is known to infect members of nine
plant families, and at least 125 individual species, including
tobacco, tomato, pepper (all members of the useful Solanaceae),
cucumbers, and a number of ornamental flowers.
The first symptom of this virus disease is a light green coloration
between the veins of young leaves. This is followed quickly by the
development of a "mosaic" or mottled pattern of light and dark
green areas in the leaves. Rugosity may also be seen where the
infected plant leaves display small localized random wrinkles.
These symptoms develop quickly and are more pronounced on younger
leaves.
Mosaic does not result in plant death, but if infection occurs
early in the season, plants are stunted. Lower leaves are subjected
to "mosaic burn" especially during periods of hot and dry weather.
In these cases, large dead areas develop in the leaves. This
constitutes one of the most destructive phases of tobacco mosaic
virus infection. Infected leaves may be crinkled, puckered, or
elongated. However, if TMV infects crops like grape and apple, it
is almost symptomless.
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