2种昆虫病原真菌对草地贪夜蛾体表侵染模式的扫描电镜观察

【目的】在前期筛选获得对草地贪夜蛾高效致病真菌球孢白僵菌（Beauveria bassiana）菌株GZSL-1和玫烟色虫草（Cordyceps fumosorosea）菌株IFCF01的基础上，进一步明确2株菌株在草地贪夜蛾体表的侵染模式，为阐明菌株致病机理，提高昆虫病原真菌对草地贪夜蛾的防效提供理论依据。【方法】利用扫描电镜观察草地贪夜蛾2龄幼虫分别接种菌株GZSL-1和IFCF01（孢子悬浮液浓度为1.0×107孢子/mL）后分生孢子在幼虫体表附着、萌发、穿透和增殖的过程。【结果】菌株GZSL-1和IFCF01萌发后均可形成附着胞，草地贪夜蛾幼虫体表结构对2株菌株分生孢子萌发、附着和穿透芽管长度有不同程度的影响。2株菌株在各结构区均有较高的萌发率（> 90.00%）和附着胞率（> 80.00%），在平缓结构区比瘤状突起结构区观察到更短的穿透芽管。在各结构区，菌株GZSL-1形成的穿透芽管长度均短于菌株IF-CF01相应的芽管长度，在平缓结构区，菌株GZSL-1的穿透芽管长度显著短于菌株IFCF01（P<0.05）。菌株GZSL-1和IFCF01分生孢子接种后分别在16和8 h内萌发，在24和32 h内普遍出现穿透结构穿透草地贪夜蛾幼虫体壁。2株菌株的初级和次级分生孢子分别在接种后72和96 h内出现。【结论】扫描电镜观察证实球孢白僵菌菌株GZSL-1和玫烟色虫草菌株IFCF01对草地贪夜蛾具有高致病性，揭示了病原真菌分生孢子在草地贪夜蛾虫体上的侵染过程，结果为后续2株菌株的改良及田间应用打下理论基础。

Mode of infection on the cuticle of Spodoptera frugiperda(Lepidoptera: Noctuidae) by two entomopathogenic fungi species revealed by scanning electron microscopy

【Objective】In this study, based on the previous screening of the high pathogenic Beauveria bassiana strain GZSL-1 and Cordyceps fumosorosea strain IFCF01 of Spodoptera frugiperda, the purpose of this study was to better understand the mode of action of these entomopathogenic fungi on the cuticle of S. frugiperda, and provide a theoretical basis for elucidating the pathogenicity mechanism of these two strains in order to achieve a constant and high control efficacy.【Method】The attachment, germination, penetration and conidial reproduction of B. bassiana and C. fumosorosea to 2nd instar larvae of S. frugiperda infected with strains GZSL-1 and IFCF01(1.0×107 conidia/mL) were observed using scanning electron microscope(SEM).【Result】Germinated conidia of both strains formed appressoria, and surface topography of S. frugiperda larvae affected germination of conidia, attachment and the length of penetrating germ tube. The two strains showed similarities in terms of high germination rate(> 90.00%) and appressoria rate(> 80.00%). There were shorter germ tubes grew before penetrating on gentle surface topography than on strumae surface topography. Strain IFCF01 exhibited longer penetrating germ tubes compared to GZSL-1 on all surface topographies. Besides, strain GZSL-1 exhibited significantly shorter penetrating germ tubes compared to strain IFCF01 on gentle surface topography(P<0.05). Strains GZSL-1 and IFCF01 began to germinate within 16 and 8 h, and penetrations were commonly observed within 24 and 32 h. After 72 and 96 h post inoculation, primary and secondary conidiophore emerged and the mycelial covered the entire cuticular surface.【Conclusion】SEM observation reveals the infection process of the highly pathogenic B. bassiana strain GZSL-1 and C. fumosorosea strain IFCF01 against S. frugiperda, the results of this study will further provide the theoretical basis and reference for strain improvement and field application.