Potato cancer disease

(pathogen name) Synchytriumendobioticum (Schilb.) Percival

(host crop) potato, tomato, Solanum nigrum, etc.

(disease diagnosis) it mainly damages the underground part of the plant, and it is common on potato tubers and stolons. The bud eyes and stolons of the killed tubers, because the bacteria stimulate the cells to divide continuously, forming tumors of different sizes, irregular shapes and rough protuberances, shaped like cauliflower. The surface of the damaged potato is often cracked. The cancer tissue was yellowish white in the early stage, green in the exposed soil surface and dark brown in the later stage. The tissue is soft, perishable and foul-smelling, with brown slime. Diseased potatoes can still develop during storage, even causing rotten cellar. Diseased potatoes turn black and give off a foul smell; after boiling for a long time, they are not easy to soften and difficult to eat. The appearance of the damaged aboveground plant was not significantly different from that of the healthy plant, but in the later stage, the diseased plant was taller than the healthy plant, the green retention period was longer, the branches were more, and the berries were more. The stems, leaves and flowers of seriously diseased plants can be damaged and form cancerous lesions or deformities. The pathogenic bacteria are endophytic kettle collecting bacteria. The bacteria are parasitic and do not produce hyphae. The vegetative bacteria are protoplasts without exposed cell walls (deformants) and then unicellular bacteria with cell walls. In the stage of reproductive growth, the monocytic cell changed to a dormant sporangium. The sporangium is nearly spherical and contains 49 sporangia. The spore sac is spherical, brown, and germinates to produce zoospores. Zoospores single flagellum, globose to pear-shaped. Some zoospores mate into zygotes. The zygote is like zoospore and double flagella, both of which can infect the host.

The pathogen overwintered with dormant sporangia in the diseased tissue or in the soil with the diseased remains. The dormant sporangium has strong stress resistance and can survive in the soil for 25 to 30 years. Under suitable conditions, it germinates and produces zoospores, invades from the host epidermis, then produces sporangia, and stimulates host cell division and proliferation. Sporangia germinate to produce zoospores or zygotes for repeated infection. The pathogen is easy to infect under the conditions of low temperature and high humidity, cool climate, large temperature difference between day and night, high soil moisture and 12-24 ℃ temperature. The land with loose soil, rich organic matter and partial acidity is easy to occur. There were differences in resistance among potato varieties.

(prevention and control measures) (1) strict quarantine. The transfer of seed potatoes from the disease area is strictly prohibited. (2) selecting disease-resistant varieties. The varieties of Mira in Yunnan show high resistance, which can be selected according to the situation. (3) reasonable arrangement of rotation. Choose grain crop rotation to eliminate interannual potatoes. Change to non-Solanaceae crops in seriously ill areas. (4) strengthen cultivation management. Avoid low-lying land prone to waterlogging, apply rotten disease-free fertilizer, increase phosphorus and potassium fertilizer, and destroy diseased and residual plants. (5) do a good job of chemical prevention and control. Use 15% trimethoprim, 400 grams per 667 square meters. Can use: ① medicine soil cover seed, after sowing with 1③ 200 medicine soil cover seed potato; ② medicine nest, when potato emergence 70%, with 1000 times liquid irrigation root; ③ medicine spray, spray once at seedling 70%, once in bud, with 1500 times liquid 60 kg every 667m2.