南瓜白粉病病原菌鉴定及寄主范围测定

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。

Hull-less pumpkin powdery mildew and its host range

The pathogen causing hull-less pumpkin (Cucurbita moschata) powdery mildew in Wuwei District of Gansu Province was identified as Podosphaera xanthii based on the morphology of cleistothecia and conidia, conidial germination and host range, etc. The results show that the optimum temperature, relative humidity and illumination for formation of cleistothecia on hull-less pumpkin were 20℃, 70% and 4,400lx, respectively. The host range test shows that the pathogen could infect many species of Cucurbitaceae except Luffa cylindrical. Triticum aestivum, Capsicum annuum, Lycopersicon esculentum, Trifolium repens, Medicago sativa, Phaseolus vulgaris (‘Jiadouwang’) and Phaseolus vulgaris couldn’t be infected. The pathogen could also attack Phaseolus radiatus, Vigna angularis and Helianthus annuus. The most susceptible plants were Cucurbita moschata, Phaseolus radiaus, Cucurbita pepo, Vigna angularis, Helianthus annuus, Cucumis melo and Cucumis sativus, their disease incidence rates reached 100%, and the disease index were 15.56, 14.51,13.33, 13.33, 13.07, 12.22 and 12.22 respectively in 15 days after inoculation. The infection process was observed. The results indicate that the conidia germinate from the lateral sides in 12 hours after inoculation, and then form hyphae in 24 hours. The hypha extended and formed net-like mycelia in 36 hours and 72 hours, and finally produced conidiophores and chains of conidia in 96 hours.