Wheat full-blown disease is a typical root disease, and full-blown disease is a devastating disease on wheat, causing clusters or large dead plants, reducing the number of effective panicles, grains per spike and 1000-grain weight, resulting in serious yield losses.
First, the onset period of wheat seedling stage and adult stage can be disease, with the symptoms of the disease strains are most obvious at the time of rapid maturation, the performance piece wheat ears back to wheat white. The pathogenic bacteria at the seedling stage mainly infested the roots and underground stems, causing them to turn black and rot. On the ground, the leaves of the diseased seedlings were yellowed, the leaves were involute, the tillers were reduced, the growth was weak, and they died severely. The diseased seedlings were delayed, sparse and sparse, and their roots became darker. After the jointing, the basal 1-2 stalk of the stem base and the surface of the stalk form a dark brown hyphae layer under the wet conditions, known as "black feet", which is the typical symptom of full erosive disease different from other root rot. The severely diseased plants showed obvious dwarfing in the shoots, and the dwarfing of the late plants was not obvious. Due to the onset of stem base, the plant sooner formed "white spikes". The diseased plants in the field were clustered or distributed in patches. In severe cases, the whole plant died. In moist conditions, when the wheat is nearly mature, there are black granular protrusions on the inside of the sheath of the base of the diseased plant, which is the ascospora shell of the pathogenic bacteria. However, under the conditions of drought, the symptoms of "black feet" at the base of the diseased plants are not obvious, and no ascostic shells are also produced.
Second, the pathogenic genus ascomycete is a subcapsule of the genus Gaeumannomyces gramims (Sacc.) Arx et Olivier.
Third, the pathogenic bacteria growth temperature range of 3-33 °C. Ascospore formation temperature is about 20 °C, and below 14 °C is not conducive to ascospore shell and ascospores. The optimum temperature for ascospore germination is 20-25°C. The optimum temperature for pathogenic infection is 12-18°C, and the soil temperature can still be infected at 6-8°C. The relatively high air and soil relative humidity required for growth and development of germs and the relative humidity of 80-90% are suitable conditions. Below 50%, the growth is slowed down, and ascospore shells are not easily generated. The bacteria have a wide range of pH adaptation, and pH 5.5-8.5 is the most suitable. The formation of the asccus shell needs illumination, and the scattering light is better in the room, and the strong illumination is not conducive to the generation of the asccus shell.
Fourth, the disease cycle (a) early infestation: The main mycelium with the disease body in the soil in summer or winter, becoming the second year of the initial infestation. Sick bodies that survive in unripened rot organic fertilizers can also serve as primary infestation sources. Fully etched pathogens in parasitic wheat seedlings, weeds, or other crops can also infect the next crop. The types of primary infestation sources mentioned above have the greatest effect on the mycelium of the diseased body. After the ascospores have fallen into the soil, their germination and infection are inhibited. Although they can cause certain diseases, their effects are far less important than the mycelium in the diseased body. Whole wheat fungal pathogens are soil inhabiting bacteria. The survival time of pathogens in soil is not consistent with the experimental conditions and methods. The results vary from 1-2 years to 3-5 years, and crop rotation can reduce the disease.
(b) Transmission: This disease is a soil-borne disease. The application of untransformed manure with diseased bodies can also spread the disease. Watering the fields, plowing ploughs, etc. result in the spread of germs at closer distances. There has been controversy over the transmission of seeds and the initial source of infection in the new ward. The so-called "seed-borne disease" generally refers to the disease-transmitting effect of mixed diseases between seeds. Mixing the diseased body into the seed or mixing the collected seed inclusions into the soil can cause disease. However, the number of mixed diseases in the production seeds is very small, and the disease-producing test using the cultivars in the wards has not been successful. Disease-free areas are prohibited from transporting seeds from the ward.
(c) The natural decline of disease: Wheat full-blown disease is a disease that has so far apparently caused natural decline. The so-called "Take-all Decline" (TAD) refers to the continuous cropping of wheat or barley in fully eroded fields. When the disease reaches its peak, the disease naturally decreases without any preventive measures. The natural decline of full-blown disease has been found at home and abroad. In the mid and late 1970s, a large area of ​​diseases in the Yantai and Wuwei areas of Shandong Province, where the full-blown disease of wheat was seriously damaged, naturally declined. There are two preconditions for the natural decline of wheat full-blown disease, one is continuous cropping, and the other is that the hazard is at its peak. Both are indispensable. The sign that the disease has reached a peak is that the white spike rate is above 60%, and the dwarfing early death center appears in the sick field. Through research and investigation, it has been found that the full-blown disease in wheat continuous cropping areas is generally severe for 3 to 3 years from sporadic disease in the field to the entire field. If the soil fertility is high, the disease development is slow, and it usually takes 6 to 7 years to reach a peak. Serious damage time varies from 1-3 years. Since then, the disease has tended to decline and stabilize. If the diseased host is interrupted by continuous cropping or soil disinfection after the occurrence of disease peaks, TAD does not appear. There are different hypotheses about the causes of the natural decay of total erosion. It is believed that Pseudomonas fluoresens (Pseudomonas fluoresens) is an important group related to the anti-microbial activity of earthworms. Pseudomonas spp. exists in soil organic matter or on the surface of nutrient-rich roots, and bacteria grow and multiply in damaged parts of the root system. The antibiotic (phenazine-1-hydroxy acid) secreted by it can inhibit all-etching bacteria. The presence of TAD in the soil has obvious antibacterial effect. If the antibacterial soil is treated with heat or fungicides, its antibacterial effect disappears, which indirectly proves that the disease deterioration mechanism is related to biological factors.
Fifth, the incidence of conditions Farming measures: wheat - corn - wheat continuous cropping is conducive to the accumulation of pathogens in the soil, the disease increased year by year, rational farming can reduce the incidence, but improper rotation will not necessarily reduce the incidence. Implement no-tillage or less tillage, reduce the aeration of the soil and reduce the incidence. Early sowing is more suitable than late.
Nutritional conditions: lack of major nutrients is conducive to the occurrence of full-blown disease, but the impact of nutrients on the occurrence of full-blown disease is more complex, it is generally believed that soil nitrogen deficiency caused by the full occurrence of full-blown erosion, the application of nitrogen fertilizer after the full-blind disease severity decreased. It has also been reported that the application of ammonium nitrogen (NH4-N) can reduce the incidence of wheat and increase the incidence of spring barley; the application of nitrate nitrogen (NO3-N) can increase the infection of full-etching bacteria and reduce yield. It is very clear that increasing the organic fertilizer and increasing the content of organic matter in the soil can significantly reduce the incidence. Severe phosphorus deficiency or imbalance of nitrogen and phosphorus in the soil is one of the important causes of the increase in damage caused by total erosion. The application of P fertilizer can promote the development of the plant roots, reduce the incidence, reduce the white panicles, and produce a significant effect. Other nutrients such as calcium also have a certain influence on the disease.
Soil properties and temperature and humidity: Sand soil has poor ability to protect fertilizer and is conducive to disease. Viscous soil, the disease is lighter. Alkaline soil disease is more important than neutral or acid soils. Winter wheat is warm in winter, and heavy rain occurs in late autumn and early spring. The irrigated land is heavier than the dry land. The high temperature and rain in the summer is conducive to the decomposition of the diseased bodies in the field, reducing the amount of bacteria and reducing the incidence of winter wheat.
Variety disease resistance: At present, there is a lack of varieties resistant to full-etching at home and abroad. Wheat and barley genera also lack available sources of resistance. There are only differences in the degree of disease.
Sixth, disease control The prevention and control of wheat full-blown disease should be based on agricultural measures, make full use of biological and chemical prevention and control measures to achieve the goal of protecting disease-free areas, controlling primary disease areas, and treating old wards.
1. Protection of Disease-Free Zones A disease-free zone is strictly prohibited from transporting seeds from the wards, and wheat stalks from the wards need not be used as packaging materials. The seeds transferred from the ward must be strictly tested and soaked with 0.1% thiophanate-methyl before sowing for 10 minutes to kill pathogenic bacteria on the seed surface.
2. Reasonable rotations in heavily afflicted areas can be used to control the risk of total erosion. Rotation in sporadic wards can delay the spread of the disease. The rotation should be based on local conditions, adhere to a 1-2 year rotation with non-host crops, such as peanuts, tobacco, tomatoes, beets, ramie, green manure and so on.
3. Balanced fertilization Organic base fertilizer was added to increase soil organic matter content, and about 100,000 kg of rotten organic fertilizer was applied per hectare. Inorganic fertilizer application should pay attention to the ratio of nitrogen, phosphorus and potassium, soil available phosphorus up to 0.06%, total nitrogen content of 0.07%, organic matter content of more than 1%, full-blown disease development is slow; available phosphorus content is less than 0.01% disease severity.
4. Biological control Wheat fields that are depleted in full-blind disease, or wheat fields that are about to decline, must implement two crops of wheat or two crops of wheat and corn one year in order to maintain the anti-bacterial and anti-bacterial effects of soil mites. In the United States, Pseudomonas fluorescens is used to prevent total etch disease, and field production increases by 30%, but the effect is not stable enough. The bio-control bacteria developed by the Chinese Academy of Agricultural Sciences and the bio-control agents developed by the Shandong Academy of Agricultural Sciences “eliminate the enemy†and “eliminate the erosion†all have efficacy.
5. Chemical control The 12% triadimenol WP was seeded at 0.02-0.03% seed weight (ai), and the disease prevention effect was good. When the 2.5% Siye seed coating agent was coated with 1:1000, it had a certain control effect on wheat whole rot disease.
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