以莱氏野村菌Nomuraea riley CQNr01菌株接种斜纹夜蛾Spodoptera litura 2龄和4龄幼虫,观察感病率,并利用荧光染色观察菌株在幼虫离体表皮上的孢子萌发和附着胞产生情况。结果显示,菌株CQNr01孢子悬液浓度为1×10^8、1×10^9孢子·mL^-1时斜纹夜蛾2龄幼虫的累计死亡率分别为86.58%和89.91%,而4龄则只有13.33%和16.67%。菌株CQNr01的孢子能够成功附着在斜纹夜蛾幼虫的离体表皮上,但孢子在2龄幼虫表皮的粘附能力优于4龄幼虫;接种24 h起两个龄期的离体表皮上均开始有孢子萌发现象并有附着胞和芽管产生,并随着接种时间的增长芽管不断伸长,但相同接种时间下孢子在2龄幼虫表皮上的萌发率和附着胞产生数量明显多于4龄幼虫表皮。研究证明菌株CQNr01对斜纹夜蛾高龄和低龄幼虫的致病力差异显著,其差异主要源于斜纹夜蛾幼虫体壁的屏障作用。%Virulence of Nomuraea riley CQNr01 against the 2^nd and 4^th instar larvae of Spodoptera litura was investigated.Spore germination and appressorium formation on isolated epidermis of S.litura was observed by fluorescence microscopy.Results indicated at the concentration of 1×10^8 and 1×10^9 spores·mL ^-1,the mortality of the 2^nd instar larvae caused by N.riley CQNr01 was 86.58% and 89.91%,respectively,while the mortality of the 4th instar larvae was only 13.33% and 16.67%.Under fluorescence microscopy,spores of CQNr01 were found adhered to isolated epidermis of the 2^nd and the 4th instar larvae,and spores germinated within 24 h post inoculation,while adhesion strength of the 2^nd instar larvae was stronger.The germ tubes grew longer and the germination rate became larger as the inoculation time went on.However,under the same inoculation time,the germination rate and the number of appressorium on the 2^nd instar larvae significantly exceeded to those on the 4^th instar larvae.The study showed that virulence of N.riley CQNr01 against the 2^nd and the 4^th instar larvae was significantly different and the epidermis may be the main reason.
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