一株球孢白僵菌的分离鉴定及其对草地贪夜蛾的致病性

草地贪夜蛾Spodoptera frugiperda(J.E.Smith)是我国于2019年新发现的一种迁飞性重大害虫。为了寻找对草地贪夜蛾有高致病性的昆虫病原真菌,本实验对采自广东省广州市华南农业大学湿地的感菌稻黑蝽Scotinophara lurida若虫僵虫进行了室内分离培养,结合形态学和rDNA-ITS序列分析,采用浸虫法研究了该菌对草地贪夜蛾各龄幼虫的致病力。鉴定结果表明该病原真菌为球孢白僵菌Beauveria bassiana,编号为GZSL-1菌株。菌株GZSL-1可侵染草地贪夜蛾6个龄期的幼虫,随孢子浓度的升高,草地贪夜蛾幼虫感病死亡率增加,当浓度达到1×10^8孢子/mL时,1~3龄幼虫的累计校正死亡率皆为100%,4龄和5龄幼虫也达到57.47%和55.06%,6龄仅25.28%。接菌6 d后1~5龄幼虫的LC 50值分别为1.32×10^3、3.42×10^3、1.01×10^4、1.61×10^5和1.23×10^7孢子/mL。幼虫LT50值随孢子悬浮液浓度增加而递减,在孢子浓度为1.0×10^4~1.0×10^8孢子/mL范围内,1龄、2龄和3龄幼虫的LT50值分别为3.58~1.69 d、4.30~1.78 d和5.70~3.12 d;浓度为1.0×10^5~1.0×10^8孢子/mL时,对4龄幼虫的LT50为5.45~4.85 d;浓度为1.0×10^7~1.0×10^8孢子/mL时,对5龄幼虫的LT50为5.04~5.02 d。上述研究结果表明,鉴定的球孢白僵菌菌株GZSL-1对草地贪夜蛾幼虫具有较强致病性,可为草地贪夜蛾微生物防治提供候选菌种资源。

Isolation and identification of a Beauveria bassiana isolate and its pathogenicity to Spodoptera frugiperda(Lepidoptera:Noctuidae)

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a newly global migratory pest to China in 2019. To enrich the resource of entomopathogenic fungi for S. frugiperda biocontrol, fungi infected Scotinophara lurida nymphs were collected from wetland in South China Agricultural University, Guangzhou City, Guangdong Province The strain were isolated, and the species was identified based on morphological and rDNA-ITS sequence analysis, the pathogenicity of the strain to S. frugiperda larvae was studied in laboratory by immersing larvae of different instars into serial concentrations of conidial suspension. Results showed that this strain was identified as Beauveria bassiana, named GZSL-1 Larvae from 1st to 6th instar were infected by B. bassiana strain GZSL-1. The mortality rates of the S. frugiperda caused by infection of B. bassiana increased with the concentration of conidial suspension and the time after treatment. The highest concentration (1×10^8 conidia/mL) treatment caused 100%, 100%, 100%, 57.47%, 55.06%, and 25.28% corrected mortality for 1st to 6th instar larvae on the 6th day, respectively. The estimated LC50 values of 1st to 5th instar larvae on day 6 after treatment were 1.32×10^3, 3.42×10^3, 1.01×10^4, 1.61×10^5, and 1.23×10^7 conidia/mL, respectively. Values of LT50 of all tested instars were shortened with concentration. The LT50 values of 1st, 2nd and 3rd instar were 3.58~1.69 days, 4.30~1.78 days, and 5.70~3.12 days, respectively, in the range of 1×10^4~1×10^8 conidia/mL The LT 50 values of 4th instar were 5.45~4.85 days in the range of 1×10.5~1×10.8 conidia/mL The LT50 values of 5th instar were 5.04~5.02 days in the range of 1×10^7~1×10^8 conidia/mL. The results suggested that the B. bassiana strain GZSL1 is a promising candidate for use in microbial control of S frugiperda.