Cotton fusarium wilt is a fungal disease caused by Fusarium oxysporum wilt specialization, which is a kind of fungus. First discovered in the United States in 1891, it has become a worldwide disease. At present, China's major cotton regions have generally occurred.
Cotton wilt can develop from the cotyledon stage, the diseased plant is short, the rate of shedding of the bells is high, the number of bolls per plant is decreased, the boll weight is reduced, and the cotton fiber strength is reduced, which affects the cotton yield and quality. Severe disease of 1-2 true leaves can cause dead seedlings. At the peak of onset budding stage, dead seedlings can be formed. The symptoms vary with environmental conditions, the type of cotton, the growth period of cotton, and the pathogenicity of pathogens. There are roughly 5 types:
(1) The typical symptom of the yellow reticulate type is that the vein catheter is yellow after being attacked by Fusarium toxin, while the leaf remains green, mostly occurring in the cotyledon and the previous true leaves. (2) Yellowing generally starts from the edge of the cotyledon or true leaf, and the mesophyll fades and turns yellow. (3) The purplish red type generally occurs when the temperature in the early spring is low, and all or part of the cotyledons or true leaves show purple spots, and the leaves fall off in severe cases. (4) Symptoms of greenish-blight-type strains in the event of a sudden loss of water, especially in arid climates, in the presence of showers, followed by high temperature and strong sunshine, the diseased leaves are dark green, the leaves become soft and drooping, and the plants are blue. Withered dead. (5) Shrinkage type Dark green leaves, thickening of leaf flesh, leaf shrinkage, shortening between nodes, dwarfing of plants, often coexist with reticulate and jaundice-type symptoms.
The pathogens of cotton fusarium wilt and verticillium wilt are different, but they all act on the vascular bundles of plants and the infection process is similar. In the cotton area, there is not only a single wilt and Verticillium disease field, but also many disease-fighting fields. Sometimes a cotton plant also infects two diseases at the same time. The main differences between Wilt and Verticillium wilt are:
(1) The onset time of wilt disease is earlier than the onset of Verticillium wilt. It usually begins in the cotyledon stage. The onset of disease is at the seedling stage and the bud stage. Verticillium wilt disease begins on the 3-4 true leaves and the onset of disease The period of flowering and bolling in July-August. (2) Cotyledons and true leaves of the wilt disease-observed diseased plants exhibited yellow reticulations, partially charred, and severely caused dead seedlings. Purple and blue-green symptoms appeared under abnormal climatic conditions; Verticillium wilt diseased leaves The mesophyll fades to gray or light yellow, the leaves look like the color and markings of the rind, the leaves turn upside down, and the deciduous flora can cause large areas of fallen leaves. (3) In the middle and later stages, the wilt disease strains are shortened between the nodes, the plants are short, the top dead or the local collaterals are dead, yellow reticulate leaves and local scorch appear in the leaves, and the red mold layer appears in the diseased part of the rainy season; verticillium wilt is generally not dwarfed, veins Without discoloration, the mesophyll fading leaves the whole leaf in a rind-like shape and the leaf margins are coked. The deciduous flora can cause deciduous light stalks. Symptoms generally appear in the lower part and develop upwards. A white mold layer appears in the diseased part of the rainy season. (4) Inspection of the color of the catheter showed that the discolored catheter was darker in color and dark brown in color; the lesion was paler and brownish in the lesion.
Fusarium oxysporum f. sp. can cause saprophytic life in the soil or on the residue of cotton plants, and it can also be parasited in cotton plants. It can not only spread with the transportation tools at a long distance, but also can spread with the operation and flowing water at close range, causing the bacteria to continuously spread and accumulate in the soil, aggravating the incidence rate and harm degree. Germs can survive in soil for 6-7 years, and chlamydospores can survive for as long as 15 years. The pathogenic bacteria invade the cotton plant from the root tip of the cotton seedlings. The hyphae and cotton strains that grow in the conduit are stimulated by pathogens to block the transport of water. The microspore spreads to the whole plant with the cotton body fluid, destroying the cells of the cotton plant, affecting Cotton growth and development.
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