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First reported by the Alternaria gypsophilae marigold Alternaria leaf spot occurred in the eastern part of Jilin Province. Detailed description of the symptoms of the disease: leaves, stems, and spend the formation of brown, purple-brown, round or irregular lesion, lesion central off-white or yellow-white, serious lesion color deepened, connecting into pieces, leaves dry stems necrosis. Three pathogenic strains of bacteria isolated from the the different diseased parts of marigold plants Gengzhi conidia or slightly bent to one side, brown, septate, have 2-3 significant spore marks. Conidia down sticks shaped, oblong, brown, initially colorless, post deepen into purple-brown, diaphragm 1-9, the mediastinal 0-9, size 17.6 to 136.4 × 8.8 to 26.4um beak 4.4 ~ 43.4um, genus Alternaria the literature control identified as Alternaria gypsophilae (Dianthus tenuis). The pathogen is newly recorded species of plant fungal diseases in China, is the first reported in the international marigold is a natural host for the pathogen. Biological assay: The results show that the bacteria can be a good use of sucrose, maltose, better utilization of sorbitol, glucose, fructose, mannitol using worst. Good sporulation sucrose and mannitol, other carbon sources sporulation low. Nitrogen source, potassium nitrate, the use of the strongest, sporulation is relatively high, and the other poor. Germs in 18 ° C -32 ° C, pH 5.03-7.62 conditions to grow well and can sporulation, 26 ℃ -28 ℃, pH 6.27-7.00 optimum growth and sporulation conditions. The carrot juice agar medium (CJA), the Hayduk medium (Hay), 10% of potato sucrose agar, the marigold plants dextrose medium (10% PSA) on mycelium cottony dense aerial hyphae, rapid growth, The largest amount of sporulation on potato sucrose agar medium (PSA), CJA followed, oatmeal agar medium (OMA), the worst carrot agar medium (CA). Little effect of light on the growth of pathogenic bacteria, but can affect the sporulation, natural light than incandescent but also to promote the role of the pathogen sporulation. Could germinate 5 ℃ -30 ℃ to 20 ℃ -25 ℃ optimal, less than 5 ° C or above 30 ℃ is not conducive to germination, the most vulnerable in spore germination in the water droplets, even if the relative humidity (RH) 100% germination rate is only about 45% of the water droplets, RH almost 75% germination. Disease pathogens could infect marigold artificial inoculation also infection maidenhair, tomato. For the first time systematically studied Occurrence of marigold Alternaria leaf spot. The results show that: the pathogen can overwinter in field and indoor sick deformed field primary infection source, and is the main source of infection, followed by seed infection. For natural orifice or direct invasion pathways of pathogenic bacteria can invade through wounds, but has little effect on the disease extended. The occurrence of disease prevalence is closely related with the temperature and humidity, under suitable temperature conditions, humidity bigger and more conducive to the disease, the humidity is the dominant factor in disease incidence and prevalence. Raise the level of nitrogen fertilizer, the incidence increased nitrogen fertilizers promote the occurrence of disease; potash level, disease refers to a corresponding decline in plant disease resistance enhanced, but the high potassium reducing disease effect is not obvious; rotation can reduce the incidence. Fungicide Screening field plot efficacy trials, screening and complex Iprodione bashing bacteria PL several ideal agents, anti-efficiency above 70%. According to the study of the occurrence regularity practical disease control measures: () Breeding resistant varieties, disease Tian saved seed. A blanket Os door) before planting 0.1O soaking 10 min, 30 min and 52 ° C hot water soaking wash with water after Primed sowing. () To clear the field the sick deformed, field the sick deformed and the disease is the main source of primary infection, revenged timely removal of the sick deformed, crop rotation or deep plowing can drive down the field early infection sources, and as far as possible in the disease control minimum damage level. (4) to strengthen the cultivation management: rational close planting, to avoid too large field humidity; N, P, K Combined Application, to avoid partial nitrogen properly enhanced potassium fertilizer to improve plant disease resistance. (5) Chemical control: the seedling stage incidence timely Pharmacy protection, in order to avoid contaminated transplanting into Daejeon; Daejeon onset available agents: 50% iprodione WP (Wp) is the 0 dilution door 50 X), SO% new million students Wp 500 X 54% before special bacteria Wp 500 X 53% more than bacteria clear Wp 500 X interval 7-10 days pesticide once, depending on the condition even applied 2-3 times. After July 20 conditional early onset of spraying, the better.
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