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Tomato Spotted Wilt Virus
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- Necrotic and/or chlorotic spots or streaks on the foliage, leaf petioles and stems.
- Plants will be pale green color and become very distorted.
- Stems may develop purplish-brown streaking.
- Stem symptoms will lead to wilting and stunting in the plant.
- Green immature tomato fruit will be mottled and have slightly raised areas with faint concentric rings.
- Mature fruit will have very distinct red or yellowish-white rings.
- Blotches with sunken areas may form.
- Necrotic ringspots form on tomato fruits with Tomato chlorotic spot virus.
There will be no visible signs on the tomato plants. However, under an electron microscope, spherical virus particles will be present consisting of three segments of negative sense RNA contained within an envelope.
Often Confused With
- Fusarium wilt – Symptoms begin with a wilt and yellowing of the leaves of older leaves. When the disease progress, the plant becomes very chlorotic and dies.
- Verticillium wilt – The older leaves are first affected and develop large yellow lesions. The plant becomes very stunted and depending on disease severity, there will be a reduction in fruit size and quantity.
- Pepino mosaic virus – Early symptoms include light green areas on the leaves and overall stunting of new growth. Chlorotic spots form on the foliage and the leaf veins turn yellow. Fruits also develop a yellow-red discoloration pattern, similar to the discoloration formed by tospoviruses.
Indicator Plant Bioassay
Tomato spotted wilt viruses is mechanically transmissible through sap inoculation. One of the most common indicator plants used to detect TSWV is the ornamental crop pentunia. Petunias are very susceptible and just four days after infection, local brown lesions form indicating infection. Petunia reacts similarly to all isolates of TSWV, which makes it a successful indicator plant. This has been described in more detail by W. R. Allen & J. A. Matteoni, 1991 (pdf).