Symptoms mainly affect the underground. Damaged tuber stems or stems of the stem due to pathogenic bacteria stimulate the continuous division of host cells, the formation of large and small cauliflower-like tumor, epidermis often cracked, cancerous tissue was yellow and white in the early stage, late dark brown, soft, perishable and produce malodour. The diseased potato can still continue to expand during the cellaring period, resulting in a rotting cellar. The diseased potato turns black and emits odor. Above ground, there was no significant difference between the early stage and the healthy strains in the field disease strains. The diseased plants in the latter stage were taller than the healthy plants, with dark green leaves and many branches. The diseased stems, stems, and leaves of some diseased plants in severely affected fields can be damaged and produce cancerous lesions.
The pathogenic Synchytrium endobioticum (Schulbersky) Percival is known as an endogenous tick bacterium or potato cancer fungus, belonging to the flagellin subphylum fungi. The pathogen is endoparasitic, and its initial vegetative bacterial flora is a mass of unexposed protoplasts (called deformed bodies), followed by cell walled monocytes. When the bacterium turns from vegetative growth to reproductive growth, the whole unicellular bacteria's protoplasts are transformed into a resting dormant sac with a total cyst wall. The sporangia sac is nearly spherical with a size of 47100 to 7881 (μm) and contains several spores. bag. The sporangia are spherical, rust-brown, with a size of 40.3-7731.4-64.6 (μm). The walls are ridged and release zoospore or zygote upon germination. Zoospore with single flagellate, globose or pear-shaped, diameter 2—
2.5 Pm, zygote with double flagellum, shape as zoospore, but larger. Can swim in water, but also for the initial infection and re-infection.
Transmission routes and pathogenic conditions The pathogens live through the resting sporangia in the diseased tissue or in the soil with the remains of the diseased body. The dormant sporocysts are highly resistant to stress, and can survive in soil for 25-30 years. When the conditions are favorable, they produce zoospores and zygotes that invade from the epidermal cells of the host and grow to produce sporangia. Sporangia can release zoospore or zygotes for repeated infection. And stimulate the host cell to continue to divide and hyperplasia. At the end of the growing season, the germs were transferred to winter through dormant sporangia. The requirements for ecological conditions of the bacteria are relatively strict, and pathogenic bacteria infested under conditions of low temperature and humidity, cold climate, large temperature difference between day and night, high soil moisture, and temperature of 12-24°C. The current disease mainly occurs in Sichuan and Yunnan, and the epidemic area is generally in the cold mountainous area with an elevation of about 2000m. In addition, soil organic matter is rich and acidic conditions favor the onset.
Prevention methods (1) Strict quarantine, delimitation of the epidemic areas and protected areas is prohibited outside the affected areas of seed potato transport, the soil of the sick fields and the plants growing on them is also prohibited from moving out. (2) The resistance of the disease-resistant cultivars differed greatly. The potato “rice†cultivars in Yunnan of China showed high resistance and could be selected according to local conditions. (3) Potatoes should not be re-planted in serious diseases. Generally, the diseased land should be changed to non-solanum crops according to actual conditions. (4) Strengthen the cultivation and management to do the intensive cultivation, use the net excrement, increase the application of phosphorus and potassium fertilizers, and promptly excavate the diseased plants and burn them in a concentrated manner. (5) Soil disinfection when necessary. (6) Early application of Pesticides to prevent and control slopes, convenient water sources in 70% of the plants emerged to the seedling stage, with 20% triadimefon EC 1500 times; water inconvenient fields can be seedling, Bud spraying 20% ​​triadimefon EC 2000 times, spraying 50-60L per 667m2 good liquid, there is a certain control effect.
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