昆虫病原真菌长孢蜡蚧菌TF-2菌株对豌豆蚜的侵染过程和致病力

Infection process and pathogenicity of entomopathogenic fungus Lecanicillium longisporum strain TF-2 to Acyrthosiphon pisum(Hemiptera:Aphididae)

【目的】豌豆蚜Acyrthosiphon pisum是世界性的重要农业害虫,给豆类作物造成巨大的经济损失。本研究在前期筛选已获得豌豆蚜致病菌长孢蜡蚧菌Lecanicillium longisporum TF-2菌株的基础上,检测了该致病菌分生孢子对豌豆蚜的毒力效用及侵染方式,以期为利用昆虫病原真菌防治豌豆蚜提供理论基础。【方法】采用离体叶片饲养法检测在不同浓度长孢蜡蚧菌TF-2菌株孢子悬浮液(1.0×103~1.0×107孢子/mL)中浸渍后对豌豆蚜成虫的致病力;应用扫描电镜和体视显微镜观察豌豆蚜成虫接种TF-2菌株(1.0×107孢子/mL)后长孢蜡蚧菌TF-2菌株侵染症状和侵染过程。【结果】不同浓度长孢蜡蚧菌TF-2菌株分生孢子浸染豌豆蚜成虫致病力随分生孢子浓度升高而逐渐增强,侵染后6 d对豌豆蚜成虫的半致死浓度(LC 50)为3.26×104孢子/mL,最高浓度分生孢子(1.0×107孢子/mL)对豌豆蚜成虫的半致死时间(LT 50)为2.92 d。扫描电镜观察结果表明,接种后24 h,TF-2菌株分生孢子在豌豆蚜成虫体表皮萌发形成芽管和附着胞;接种后48 h,芽管伸长在复眼、触角基部、足基节、腹末生殖节等部位形成网络结构;接种后96 h,菌丝布满整个虫体,新的分生孢子产生。【结论】长孢蜡蚧菌TF-2菌株对豌豆蚜成虫具有较强的致病力,扫描电镜观察揭示了其分生孢子在其虫体上的侵染过程,结果为进一步应用昆虫病原真菌进行生物防治提供理论基础和参考依据。

【Aim】The pea aphid,Acyrthosiphon pisum,is an important agricultural pest in the world and causes great economic losses to legume crops.In this study,based on the previous screening of the pathogen Lecanicillium longisporum strain TF-2 of A.pisum,the virulence effect and infection mode of conidia of this pathogen on A.pisum were detected,so as to provide a theoretical basis for the control of A.pisum by entomogenic fungi.【Methods】The pathogenicity of L.longisporum strain TF-2 to A.pisum adults dipped into serial concentrations of conidial suspension(1.0×103-1.0×107 conidia/mL)of L.longisporum strain TF-2 was assayed by feeding method with detached leaves in the laboratory.The external infection symptoms and process of L.longisporum strain TF-2 to A.pisum adults infected with the TF-2 strain(1.0×107 conidia/mL)were observed under scanning electron microscope(SEM)and stereoscopic microscope(SM).【Results】The pathogenicity of different concentrations of conidia of L.longisporum strain TF-2 to A.pisum adults gradually enhanced with the increase of conidial concentration.The medium lethal concentration(LC 50)of the TF-2 strain to A.pisum adults at 6 d after treatment was 3.26×104 conidia/mL,and the medium lethal time(LT 50)of this strain at the highest treatment concentration(1.0×107 conidia/mL)was 2.92 d.The results of SEM observation showed that the conidia of L.longisporum strain TF-2 germinated and bud tubes and appressorium formed on the epidermis of A.pisum adults at 24 h after inoculation.Bud tubes elongated and a network structure formed in compound eyes,the base of antennae,the basal segment of legs,the end of the abdomen reproductive segment,etc.of A.pisum adults,at 48 h after inoculation.At 96 h after inoculation,hyphae covered the whole body of A.pisum adults and new conidia produced.【Conclusion】L.longisporum strain TF-2 has a strong pathogenicity to A.pisum adults,and the SEM observation revealed the infection process of its conidia.These results provide the theoretical basis and references for the further application of entomogenous fungi in biological control.