Abundant moisture and frequent rains favourable for this disease.Penetration occurs most frequently through the junction of epidermal cells.Wind, rains, and insects are the major spreading agents. Infection: Primary spots are the site of secondary spread of the disease. Penetration: Mode of penetrations are, stomata, direct through cuticle or through wounds.Conidia forms during periods of warm rainy, and humid weather conditions through conidia. Infection: Lower leaves are the site of first infection.Hence we can say, host seed is the primary source of inoculum. Mycelium and conidia are the primary cause of infection.Ĭontamination of tubers with conidia or mycelium is another source of primary inoculum. Conidia may remain viable for up to 17 months at room temperature. Mycelium remains viable in dry leaves for a year. The fungus is resistant to dry and hot weather. Moist weather favours germination of conidia. They develop from a apical cell bud of the conidiophores. Conidia born singly on the conidiophores. Melanins play role in the development of conidia. Melanins are dark, brown to black, and high molecular weight pigment. It emerges from the dead centres of the spots. The hyphae in the host are at first intercellular which penetrate the cell later.Intra cellular mycelium: It also consists of septate and branched, light brown hyphae.Inter cellular mycelium: It consists of septate and branched, light brown hyphae.Production of melanin especially in the spores, and the production of host species toxin. These may cause collapse of of the entire plant above the ground.Potato stem show brown to black necrotic lesions on the skin.Leaves shrivel and fall off in severe attack.In humid conditions, the spots coalesce and big rotting may appear.Spots turn hard in dry season and the leaves curl.It is translocated through the veins.Ĭurling of leaves and formation of rotting patches This is due to the diffusion of fungal metabolites like the toxin alternaric acid. What is the cause of yellow zone around the lesions? The symptom of chlorotic is more when spots are present in veins. Size of this chlorotic zone depends on the size of target board. Further, this chlorotic zone turns into the normal green. Presence of a narrow chlorotic zone around the spots is also a symptom of this disease. Unfavorable weather conditions are the cause of interruption of fungal growth. It is due to interruption of fugal growth. What is the cause of target board symptom? This is the most characteristic symptom of ealry blight of potato. In the necrotic area of the spots, some concentric ridges develop which form a target board. First attack appears on the leaves near the soil surface, now it progresses upward. There is a deep greenish-blue growth of fungus on these spots. Symptoms of early blight of potatoĪt first, we see small, pale brown, and scattered spots on the leaflets. Potato, tomato, and chilli are the three major host of the causal organism of this disease. Important points about disease cycleĪlso read: Olericulture (Vegetable Science) MCQ (Multiple Choice Questions) (1). Hence, it is common in hills as well as in the plains.Īlso read: What is Seed Plot Technique in Potato? Contents It is a disease of cool as well as warm regions. The disease appears at the early or young stage of plant. Damage is more severe when attack occurs during the time of tuber formation. It can cause up to 40% loss in yield of tubers. Although, the intensity of latter is comparatively less. Identify the symptoms to control or manage it. Early blight of potato is a very common disease in India, the other important disease of potato is late blight of India. A potato grower has to follow effective control measures against the early blight of potato to avoid severe loss in total crop production. It is one of common and the most important anamorphic fungal disease in the potato growing regions. Early blight of potato cause, symptoms, and control
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