Tomato virus diseases are a significant threat to tomato crops, causing various symptoms that can severely impact yield and quality. The most common symptoms include the mosaic type, characterized by mottled yellow and green leaves, translucent veins, slightly curled or shriveled leaves, and stunted growth. Another symptom is the fern leaf type, where plants become dwarfed, upper leaves turn linear, and middle and lower leaves roll up. In some cases, flowers may become abnormally large, and streaks can appear on leaves, stems, and fruits. Additionally, brownish mottles or moire patterns on leaves, black-brown stripes on vines, and irregular plaques on stems and fruits are also observed. Other symptoms like giant sprouts, leaf curling, and yellow top may occur under certain conditions. There are over 20 different viruses that cause tomato virus diseases, including Tobacco Mosaic Virus (ToMV), Cucumber Mosaic Virus (CMV), Tobacco Leafroll Virus (TLCV), and Alfalfa Mosaic Virus (AMV). Each of these viruses has distinct characteristics and causes varying symptoms. ToMV is primarily responsible for mosaic symptoms in tomatoes. It can also cause streak symptoms when combined with other viruses or under high temperature and strong light conditions. The virus has a rod-shaped structure, measuring approximately 280 nm in length and 15 nm in width. It is inactivated at temperatures between 90-93°C within 10 minutes, and it can be diluted up to 1,000,000 times. In vitro, it remains infectious for 72-96 hours. Under aseptic conditions, it can survive for several years, and in dry diseased tissue, it can persist for more than 30 years. Different strains of ToMV can lead to varied symptoms, especially when co-infected with other viruses. Cucumber Mosaic Virus (CMV) mainly causes cane-like leaf symptoms. Its particles are spherical, with a diameter of about 35 nm. It is inactivated at 65-70°C for 10 minutes, and its dilution limit ranges from 1,000 to 10,000 times. In vitro, the virus remains active for 3-4 days. CMV can also cause streaks or mosaic symptoms when combined with other viruses, leading to a wide range of visible effects. Another pathogen is a mycoplasma-like organism found in the phloem, sieve tubes, and companion cells of infected tomato plants. These organisms are nearly round, oval, dumbbell-shaped, or irregular in shape, measuring between 147-195 nm in one dimension and 240-390 nm in another. Their unit membrane is about 11 nm thick. Tobacco Leafroll Virus (TLCV) causes leaf curling and is limited in its host range, primarily affecting Solanaceae and Asteraceae plants. The virosomes are spherical, with dimensions of 25-30 nm in diameter and 15-29 nm in length. TLCV is transmitted by whiteflies and not through sap. It is commonly found during hot seasons in both southern and northern regions. Alfalfa Mosaic Virus (AMV) is a bacillus-like virus with a diameter of 18 nm and a length of 58.3 nm. It infects a wide range of hosts, including legumes, Solanaceae, Cucurbitaceae, and others. AMV has a dilution limit of 1,000 to 100,000 times, and it is inactivated at 55-60°C. It remains active for 3-4 days in vitro. The prevalence of these viruses varies by season and region. In Beijing, ToMV is most common in winter and spring, while CMV dominates in summer and autumn. From mid-May onward, CMV becomes more prevalent, accounting for about 30% of cases. ToMV alone accounts for 31.1%, while combinations such as TMV + CMV (25%) and TMV + PVX (5.8%) are also common. Overwintering sources of these viruses include infected plants, seeds, and soil residues. Infected tobacco leaves and perennial weeds serve as primary infection sources. Tomato viruses are mainly spread through sap contact, entering the plant through wounds. CMV is often transmitted by aphids, while ToMV can also spread through mechanical inoculation. Environmental conditions such as high temperature and drought favor disease development. Overuse of nitrogen fertilizer, soft plant tissues, compacted soils, and poor drainage further increase susceptibility. The types of viruses present in a given year vary, with ToMV being more prevalent in spring and summer, and CMV more common in autumn. Effective prevention and control strategies should focus on reducing virus sources and implementing integrated management practices. Prevention and control measures include selecting resistant varieties, seed disinfection, crop rotation, proper fertilization, and early application of antiviral agents. Resistant varieties such as Jiafen 15, Zhongza No. 9, Lanyouzaohong, and Su Kang 5 are available for ToMV resistance. For CMV, varieties like Hair Powder 802 and 542 Pink Tomato are recommended. Seed treatment methods include soaking in water for 3-4 hours, followed by a 30-50 minute soak in 10% trisodium phosphate solution, or using 0.1% potassium permanganate for 30 minutes. Crop rotation for more than two years, deep plowing, and lime application help reduce virus persistence in the soil. Cultivation techniques such as balanced fertilization, timely planting, weed control, and proper irrigation enhance plant resilience. Early application of antiviral solutions like 1.0% plant disease emulsion, 20% virus A WP, or antiviral agents can help manage outbreaks. Insect control is also essential, especially for preventing TMV transmission. Spraying 20% chrysanthemum EC at 2000 times dilution or 50% anti-inferiority WP at 3000-3500 times can effectively control pests and reduce virus spread. Proactive monitoring and timely intervention are key to managing tomato virus diseases successfully.

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