白僵菌菌株分离培养及对四种重要害虫的致病力

Isolation and culture of Beauveria bassiana and its pathogenicity to four important pests

【目的】从田间自然感病致死的暗黑鳃金龟HolotrichiaparallelaMotschulsky幼虫虫体中获得一株虫生真菌,明确该菌株的种类、培养特性及其对4种重要农业害虫的致病力,以期获得高毒力生防菌株。【方法】采用培养基分离纯化培养菌株,在显微镜下进行形态鉴定,并观察菌落的生长特征,测定其生长速率、孢子产量和孢子萌发率;采用生物测定法,测定菌株对害虫的致病力。【结果】确定该菌株为球孢白僵菌,在PDA和SDAY培养基上的菌落特征存在形态差异;在PDA培养基上的生长速率显著高于SDAY上的,孢子萌发率则显著低于SDAY上的,但在PDA和SDAY上的产孢量差异不显著。球孢白僵菌对亚洲玉米螟Ostrinia furnacalis Guenée幼虫和二化螟Chilo suppressalis Walker幼虫的致病力最强,显著高于黄地老虎Agrotis segetum Schiffermüller和粘虫Mythimna separata Walker的;对同一种害虫5龄幼虫的致病力均大于2龄幼虫,其中,对黄地老虎和粘虫高龄幼虫的毒力显著高于低龄幼虫的。【结论】本研究获得一株球孢白僵菌,对重要的农业害虫二化螟、亚洲玉米螟、黄地老虎和粘虫幼虫均有致病性,但致病力存在显著差异;对高龄幼虫的致病力大于低龄幼虫。感染二化螟、亚洲玉米螟幼虫最大校正死亡率可达94%以上,表明该菌株具有较大的应用潜能,适用于田间靶标害虫的生物防治。

[Objectives]A strain of entomogenous fungi was obtained from dead Holotrichia parallela Motschulsky larvae collected in the field,and its species and culture characteristics,as well as its virulence to four important agricultural pests,were measured and compared.[Methods]Fungal growth media were purified and cultured,and fungal morphology identified under a microscope.The colony growth characteristics of the fungal strain was observed,and its growth rate,spore yield and germination rate determined.The pathogenicity of the strain to the four pest species was determined by bioassay.[Results]The fungus was identified as Beauveria bassiana.Morphological differences in colony characteristics were apparent between fungal colonies cultured on PDA vs SDAY media.The growth rate on PDA was significantly higher than on SDAY,but the spore germination rate was significantly lower.The two media did not differ significantly in sporulation rate.The fungal strain was most pathogenic to Ostrinia furnacalis and Chilo suppressalis larvae,which were significantly more sucesptible to it than Agrotis segetum and Mythimna separata.The fungus was most virulent to 5 th instar larvae of the same pest species than to 2 nd instar larvae,and it was significantly more virulent to older instars of Agrotis segetum and Mythimna separata than to younger instars.[Conclusion]B.bassiana is pathogenic to the larvae of important agricultural pests such as Chilo suppressalis,Ostrinia furnacalis,Agrotis segetum and Mythimna separata,but its pathogenicity varies between species and instars.Nonetheless,the maximum corrected mortality of Chilo suppressalis and Ostrinia furnacalis larvae after infection with this fungal strain was>94%,which indicates that it has potential as a biological control for these pests.