苜蓿银纹夜蛾核型多角体病毒在宿主草地贪夜蛾选择压力下的毒力和基因变异

草地贪夜蛾Spodoptera frugiperda(J.E.Smith)原产北美,现已入侵中国许多地区,造成了巨大的生态和经济损失.杆状病毒是多种昆虫的病原体,对非目标生物无毒无害,是很有应用前景的生物农药,其施用可大大减缓草地贪夜蛾对化学农药抗性产生速度.以往的研究发现,虽然苜蓿银纹夜蛾核型多角体病毒(Autographa californica multiple nucleopolyhedrovirus,AcMNPV)可感染许多种鳞翅目昆虫,但对草地贪夜蛾口服感染能力较差.选择毒力增强的变异体是提高AcMNPV作为病毒杀虫剂应用的一个新方向.在本研究中,使用野生型AcMNPV在草地贪夜蛾2龄末幼虫中连续传代20次,并对亲本和后代分离株的毒力进行了评价.与野生型AcMNPV相比,后代分离株对草地贪夜蛾2龄末幼虫毒力显著提高.由于病毒的复制依赖于宿主细胞,受到草地贪夜蛾选择压力的影响,AcMNPV的基因发生变异.宿主适应性强的毒株在草地贪夜蛾体内的感染增殖能力较强,容易获得生长优势并成为优势毒株.更进一步,本研究通过二代测序分析了突变的关键基因.本研究可为生物农药生产提供高毒力毒株,也可在草地贪夜蛾应急防控和持续防控中发挥重要作用.

Virulence and genetic variation of Autographa californica nucleopolyhedrovirus under selection pressure of Spodoptera frugiperda

Spodoptera frugiperda (J. E. Smith), native to North America, has invaded many regions in China, causing enormous ecological and economic losses. Baculoviruses are pathogens of lots of insects, which are safe to non-target organisms with potential application as a biopesticide. Application of baculoviral insecticides can greatly slow down the resistance of S. frugiperda to chemical pesticides. Previous studies had found that although Autographa californica multiple nucleopolyhedrovirus infects many lepidopteran species, it was less effective against S. frugiperda by oral infection. Screen of virulence-enhancing variants was an attractive option to improve the application of AcMNPV as a viral insecticide. In this study, wild type AcMNPV was serially passaged 20 generations in the late 2 nd instar larvae of S. frugiperda, and the virulence of parental and progeny isolates was evaluated. Compared with the wild type AcMNPV, the virulence of the progeny was remarkably increased. Since viral replication depends on the host cells, the viral gene mutations of AcMNPV were affected by the selection pressure of S. frugiperda. The sub-strains with high survival fitness had strong infection and proliferation ability in S. frugiperda, and were easy to obtain growth advantages and become dominant sub-strains. Furthermore, the key genes for mutation were analyzed by genome-wide sequencing. This study can provide highly virulent strains for biological pesticide production, and also play an important role in emergency prevention and sustainable control of S. frugiperda.