一种斜纹夜蛾新型病原菌的分离与鉴定

Isolation and Characterization of New Pathogen from Spodoptera litura

采用10倍系列稀释法从罹病斜纹夜蛾虫尸内分离出球状病原细菌IAM1218菌株,并按Kcoh规则进行侵染试验,同时,采用菌液PCR法扩增菌株的16S rDNA序列,在GenBank数据库中进行同源序列搜索,通过Bootstrap analysis法进行1000次重复抽样分析和Neighbor-Joining法构建分支系统树分析等,结果表明,该菌株各浓度处理的斜纹夜蛾幼虫死亡率均较高,最低达(83.22±4.72)%,LT50值最高为(24.50±1.08)h;罹病幼虫体色变黑,体壁易破裂流出粘稠状物质;IAM1218菌株(GenBank No.KC790981)和酪黄肠球菌Enterococcus casseliflavus的16S rDNA区序列完全相同,相似性为100%,且二者聚类在一组,概率100%。综合分析确定该菌株为酪黄肠球菌Enterococcus casseliflavus,属于一种新型的斜纹夜蛾致病病原细菌。这为斜纹夜蛾的生物防治提供了新的技术途径。

Pathogenic coccus was isolated from a diseased larva of Spodoptera litura which perisoma became black and easy ruptured using the spread -plate technique in a series of 10 -fold dilutions, and the infection test was dealed with healthy larvae according to the Koch＇ s postulates. Subsequently, the 16S rDNA sequence of IAMI218 strain was obtained by PCR amplification, and the phylogenetic trees were founded based on some I6S rDNA sequence data of Enterococcus spp. from GenBank by Bootstrap analysis and Neighbor -Joining method. This result indicated that about （83.22± 4.72）% of the larvae died in 30h after infection and LTs0 didn＇t ex- ceed （24.50 ±1.08）h. The sequence comparison of the Enterococcus clearly shows that IAM1218 isolate was clustered to the Enterococcus casseliflavus clad rather than others. So IAM1218 strain which is a new pathogen to Spodoptera litura was identified as Enterococcus casseliflavus by 16S rDNA sequence （ GenBank No. KC790981 ）. The new technique was probably provided for alternatives biocontrol pathway to Spodoptera litura.