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通过对南瓜白粉病病原菌的闭囊壳、分生孢子及萌发方式的观察和鉴别寄主感病反应鉴定,结果表明引起甘肃省武威地区南瓜白粉病的病原菌为苍耳单囊白粉菌Podosphaera xanthii。该白粉病菌闭囊壳形成的最适条件为温度20℃、相对湿度70%和光照强度4,400lx。寄主范围测定结果表明,该病菌不侵染丝瓜、小麦、辣椒、番茄、苜蓿、红三叶草、架豆和菜豆,可侵染除丝瓜之外的其余9种瓜类植物和绿豆、红小豆、向日葵,其中对南瓜、绿豆、西葫芦、红小豆、向日葵、甜瓜和黄瓜的致病性最强,发病率均达到100%,病情指数分别为15.56、14.51、13.33、13.33、13.07、12.22和12.22。侵染过程观察发现,感病南瓜人工接种白粉菌12h后,分生孢子芽管从侧面萌发,于24h芽管伸长,于36h形成菌丝,于72h形成稠密的网状菌丝,于96h形成分生孢子梗及串生分生孢子。
The results showed that the pathogen causing pumpkin powdery mildew in Wuwei area of Gansu Province was Podosphaera xanthii, which was caused by the observation of the closed shell, conidia and germination of pumpkin powdery mildew pathogen and the identification of the host susceptible reaction. The optimum conditions for the formation of powdery mildew capsid shell were temperature 20 ℃, relative humidity 70% and light intensity 4,400lx. Host range measurement results show that the bacteria do not infect loofah, wheat, pepper, tomato, alfalfa, red clover, shelled beans and beans, other than gourd can invade the remaining nine kinds of melons and mung beans, red bean, sunflower Among them, the pathogenicity of pumpkin, mung bean, zucchini, adzuki bean, sunflower, melon and cucumber was the strongest with the incidence of 100% and the disease index of 15.56, 14.51, 13.33, 13.33, 13.07, 12.22 and 12.22 respectively. Infection process observation found that the susceptible pumpkin artificial inoculation powdery mildew 12h, conidiophore germination from the germination of the germ tube in 24 hours elongation at 36h to form mycelium in 72h to form a dense reticular mycelium at 96h Formation of conidiophores and peanut conidia.