| It is the first report about the occurrence of marigold leaf spot caused by Alternaria gypsophilae in eastern region of JiLin Province in China.The major symptoms of the diseased were described. It initially appear as circular, brown lesions with gray-white or yellow-white in center on leaves, stems and petals. Severely these lesions gradually turn dark brown or black, connect each other and eventually lead to death of very diseased sites.Three pathogenetic strains were isolated from different diseased sites and parts of marigold. Conidiophores are straight, or little curved, brow, septate. Conidia are clavate or ovate, brow, primarily colorless, gradually fuscous, 17.6 ~1 36.4 * 8.8 ~ 26.4 urn with 1-9 transverse and 0-9 longitudinal septa and their beaks are 4.4-43.4 um long. In view of the morphology and comparison with other concerned Alternaria species, the pathogens are identified as Alternaria gypsophilae.The pathogen is a new record specie of plant fungi disease in China. Marigold is a new natural host of the pathogen in the world.The biological test showed that these pathogens can utilize sucrose, maltose very well, utilize sorbierite, dextrose, levulose, while mannitol poorly. More spores were produced on sucrose and mannitol. In addition, the pathogens grew quickly and formed more spores on potassium nitrate than other nitrogen sources. At 18癈-32癈 and pH 5.00-7.00, the pathogens can grow and form spores, and the optimal condition is at 26癈-28癈 and pH 6.27-7.00. On carrot-juice agar ( CJA ), Hayduk ( Hay ), 10% potato-sucrose agar and juice of marigold (PSA), the mycelia are wooly and aerial mycelium are abundant. The capacity of producing spores was highest on PSA, secondly on CJA, least on oatmeal agar (OMA) & carrot agar (CA). The conidia can germinate at 5癈-30癈, 20癈-25 癈 was optimum. Light influence little on pthogens growth, but can affect the prduction of conidia, the natural light can accelerate the production of spores.The pathogens can infect maindenhair and tomato besides marigold at inoculated.The regularity of the disease are reported firstly in JiLin Province. The results indicated that the primary infection sources mainly come from marigold refuse in soil, secondly from infected seeds. They could infected plants through natural orifirce or directly, wound is one of the infection routes but not main one. The occurrence of the disease is closely correlated with weather conditions, amount and kind of fertilizers ,the crop rotation. Relative humidity is the vital factor of weather conditions in the disease epidemic.The more effective fungicides were chose or developed, such as " 50% iprodione wp", "80% mancozeb wp", "54% Pu Jun Te wp", "53% Duo Jun Qing wp", their control effect are almost above 70%.According to studies on the occurrence regularity of the disease, integrated control measures have been put forward ,which show good control effect in the field in Dunhua of Jilin province. These measures include breeding and cultivating resistant-disease varieties, infecting seeds with 0.1%AgNO3, cleaning away marigold refuse in the field, enhancing cultivation management, increasing potash fertilizer properly and spraying "50% iprodione wp 750x", "80% mancozeb wp 500*" "54% Pu Jun Te wp 500*", "53% Duo Jun Te wp 500*" at the early period of the disease occurrence.
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