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What is Tobacco ringspot virus disease of Carnation?

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(Tobacco ringspot virus disease of Carnation) [Symptoms] Mottling, mild mosaic and plant decline appear on the affected leaf areas. [Pathogen] Tobacco ringspot virus (Tobacco ringspot Nepovirus, TRSV). It belongs to the family Secoviridae, genus Nepovirus. The virus particles are spherical, about 28 nm in diameter. The virus mainly has 3 types of particles: empty shells without RNA (T), non-infectious nucleoprotein (M), infectious nucleoprotein (B), and a satellite-like particle (SL), with sedimentation coefficients of 535 (T), 915 (M), 1265 (B), and 1225 (SL), respectively. The satellite is 359 nt in size. The coat protein accounts for 60% of the particle weight, and the nucleic acid accounts for 40% of the particle weight; it is single-stranded RNA, and the genome consists of 2 types of RNA, namely RNA1 and RNA2, with molecular weights of 2.73 x 106 and 1.34 x 106, respectively. The RNA1 genome is 7514 nt. The sedimentation coefficients are 32S for RNA1 and 24S for RNA2. When diluted 1:5 with distilled water, the thermal inactivation point is 65 degC, the dilution end point is 0.001-0.0001, and the longevity in vitro is 6-10 d at room temperature, 3 weeks at 18 degC, loses infectivity after several months at 2 degC, and retains activity after 10 years of storage under sealed conditions as a frozen low-temperature liquid; leaves dried with calcium chloride remain infectious after storage at -10 degC for more than 1 year. TRSV has good immunogenicity, and antiserum with a titer above 1:2000 is easily obtained; it has no serological relationship with viruses of the same genus, such as Tomato ringspot virus and Arabis mosaic virus.

　　(TobaccoringspotvirusdiseaseofCarnation)

[Symptoms] Mottling, mild mosaic and plant decline appear on the affected leaf areas.

[Pathogen] Tobacco ringspot virus (Tobacco ringspot Nepovirus, TRSV). It belongs to the family Secoviridae, genus Nepovirus. The virus particles are spherical, about 28 nm in diameter. The virus mainly has 3 types of particles: empty shells without RNA (T), non-infectious nucleoprotein (M), infectious nucleoprotein (B), and a satellite-like particle (SL), with sedimentation coefficients of 535 (T), 915 (M), 1265 (B), and 1225 (SL), respectively. The satellite is 359 nt in size. The coat protein accounts for 60% of the particle weight, and the nucleic acid accounts for 40% of the particle weight; it is single-stranded RNA, and the genome consists of 2 types of RNA, namely RNA1 and RNA2, with molecular weights of 2.73 x 106 and 1.34 x 106, respectively. The RNA1 genome is 7514 nt. The sedimentation coefficients are 32S for RNA1 and 24S for RNA2. When diluted 1:5 with distilled water, the thermal inactivation point is 65 degC, the dilution end point is 0.001-0.0001, and the longevity in vitro is 6-10 d at room temperature, 3 weeks at 18 degC, loses infectivity after several months at 2 degC, and retains activity after 10 years of storage under sealed conditions as a frozen low-temperature liquid; leaves dried with calcium chloride remain infectious after storage at -10 degC for more than 1 year. TRSV has good immunogenicity, and antiserum with a titer above 1:2000 is easily obtained; it has no serological relationship with viruses of the same genus, such as Tomato ringspot virus and Arabis mosaic virus.

[Disease development] The virus is transmitted by sap and seed, and there are many seed-transmitting hosts, such as melon, globe amaranth, lettuce, cowpea, dandelion, tobacco and common groundsel. In addition, potato, zinnia, geranium and others are all transmitted through seed. The main transmission vector is the adult and 3rd-instar larva of Xiphinema americanum in the soil. A single nematode can also transmit the virus. The nematode acquires the virus within 24 h. Infected nematodes can still transmit the virus after being stored at 10 degC for 49 weeks. In addition, thrips nymphs, mites, leafhoppers, tobacco leaf beetles and green peach aphids can also transmit the virus.

[Control]

1. Strengthen quarantine and prohibit the import of diseased seeds, bulbs and seedlings from affected areas.

2. Apply nematicides to eliminate nematodes in the soil; use insecticides to kill thrips, grasshoppers, leaf beetles and aphids. For nematodes in the soil, D-D mixture can be applied to the soil or ethoprophos can be used for soil treatment. For thrips, grasshoppers, leaf beetles and aphids, insecticides can be sprayed. Commonly used insecticides include 50% malathion emulsifiable concentrate at 1000 times dilution, 40% dimethoate emulsifiable concentrate at 1000-1500 times dilution, compound fruit emulsifiable concentrate (40% dichlorvos, 10% omethoate) at 2000-3000 times dilution, 20% fenpropathrin emulsifiable concentrate at 3000 times dilution, 50% fenitrothion at 1000 times dilution, 25% carbaryl at 400 times dilution, etc.

3. Crop rotation and weed control. Rotating with non-host crops for 1-2 years can eliminate or reduce nematodes in the soil; clearing weeds can eliminate transmission vectors and sources of infection.

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