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1981.7,首次在花溪桐木岭发现了三株向日葵霜霉病病株,随后在附近续有发现。用平行线取样法检查了450株,病株为104株,发病率为23.1％病株矮缩,有的在开花前死去,或虽能开花,但不结子。症状:株高只为健株的1/4～1/2,叶片病斑不规则,沿主脉和支脉两侧发展,病叶黄绿相间,略皱缩而质脆,病斑上有较厚的白色霉层,有时茎和花器上也有白粉霉状物。天气干燥则病征不明显。病原菌经鉴定为Plasmopara halstedii(Tarl)Berl de Tonl孢囊梗自气孔伸出,无色,单轴分
In 1981.7, three sunflower downy mildew strains were found for the first time in Tongmuling, Huaxi, and subsequently found in the vicinity. A total of 450 strains were examined by the parallel line sampling method. The number of diseased plants was 104, with a disease rate of 23.1%. The plants were dwarfed and some died before flowering, or they could flowering but did not knot. Symptoms: plant height of only 1/4 ~ 1/2 of healthy plants, leaf lesions irregular, along the main vein and branch vein on both sides of development, diseased leaves yellow-green and white, slightly shrinkage and crisp, lesions are more Thick white mildew layer, sometimes stems and flowers also powdery mildew. Dry weather is not obvious symptoms. The pathogen was identified as Plasmopara halstedii (Tarl) Berl de Tonl cyst stems protruding from the stoma, a colorless, uniaxial