广州地区一株绿僵菌的鉴定及其对草地贪夜蛾的致病力测定

Identification of a Metarhizium strain and its pathogenicity to Spodoptera frugiperda(Lepidoptera:Noctuidae)in Guangzhou area

【目的】寻找草地贪夜蛾(Spodoptera frugiperda)致病性昆虫病原真菌,以丰富广东省本地的昆虫病原真菌资源库,为开展草地贪夜蛾微生物防治提供研究材料。【方法】对采自广东省广州市增城区荔城镇玉米地的感菌草地贪夜蛾幼虫体表病原真菌进行微生物常规分离纯化,采用形态学和ITS-rDNA序列分析相结合的方法对病原真菌进行鉴定,通过3种不同培养基(PDA、SMAY和添加草地贪夜蛾蛹壳PDA培养基)测定病原真菌菌落生长速率和产孢量,并采用浸虫法研究病原真菌对草地贪夜蛾2龄幼虫的致病力。【结果】从感菌草地贪夜蛾幼虫上分离获得病原真菌,编号GZSF-1,经鉴定为莱氏绿僵菌(Metarhizium rileyi)。培养基类型对菌株GZSF-1菌丝生长和产孢存在显著影响(P<0.05),菌株在各培养基上的生长速率为0.76~2.10 mm/d,产孢量为0.33×106~21.67×106孢子/mL,其中在添加蛹壳PDA培养基上的生长速度最快且可获得最大产孢量。菌株GZSF-1接种草地贪夜蛾2龄幼虫后,随孢子悬浮液浓度的升高,幼虫的感病死亡率增加,当浓度达1×109孢子/mL时,幼虫的致死中时(LT50)为3.030 d,接菌7 d后幼虫的累计校正死亡率达100.00%。应用Probit模型,得到菌株GZSF-1对草地贪夜蛾2龄幼虫的致病力回归方程y=-4.426+0.737x,菌株GZSF-1对草地贪夜蛾2龄幼虫第7 d的致死中浓度(LC50)为1.02×106孢子/mL。【结论】从田间感菌草地贪夜蛾上分离获得的病原真菌菌株GZSF-1为莱氏绿僵菌,该菌株对草地贪夜蛾幼虫具有较好的生防潜力,具有进一步研究的价值。

【Objective】The pathogenic fungi against Spodoptera frugiperda were screened to enrich the resource of entomopathogenic fungi in Guangdong for S.frugiperda biocontrol.【Method】Fungi infected S.frugiperda larvae were collected from corn field in Licheng Town,Zengcheng District,Guangzhou City,Guangdong Province.The strain were isolated by using conventional separation and purification method,the species was identified based on morphological and ITS-rDNA sequence analysis,growth and sporulation of the strain were observed on three different culture media(PDA,SMAY,and PDA medium containing puparium powder),and the pathogenicity of the strain to S.frugiperda larvae was studied in laboratory by immersing 2nd instar larvae into serial concentrations of conidial suspension.【Result】The pathogen isolated form the infected larvae was identified as Metarhizium rileyi,numbered as GZSF-1.The type of culture media had significant influence on mycelial growth and sporulation of strain GZSF-1(P<0.05).The growth rate of the strain on different media was 0.76-2.10 mm/d,and sporulation was 0.33×106-21.67×106 conidia/mL.The strain GZSF-1 had good adaptability to PDA medium contained puparium powder with the fastest growth rate and largest sporulation.The mortality rates of the 2nd instar larvae caused by infection of M.rileyi strain GZSF-1 increased with the rising of concentration of conidial suspension.When the concentration reached 1×109 conidia/mL,the median lethal time(LT50)was 3.030 d.The corrected accumulative mortality for 2nd instar larvae after 10 d was 100.00%.The regression equation of the pathogenicity of strain GZSF-1 to 2nd instar larvae was y=-4.426+0.737x by using Probit model.The median lethal concentration(LC50)value of strain GZSF-1 to 2nd instar larvae on day 7 was 1.02×106 conidia/mL.【Conclusion】The pathogen strain GZSF-1 isolated form the infected larvae was identified as M.rileyi.It has potential biocontrol effects against S.frugiperda and worth further research.