Popham Holly J R, Rowley Daniel L, Harrison Robert L
Biological Control of Insects Research Laboratory, USDA Agricultural Research Service, 1503 S. Providence Road, Columbia, MO 65203, USA.
Invasive Insect Biocontrol and Behavior Laboratory, Beltsville Agricultural Research Center, USDA Agricultural Research Service, 10300 Baltimore Avenue, Beltsville, MD 20705, USA.
J Invertebr Pathol. 2021 Jul;183:107561. doi: 10.1016/j.jip.2021.107561. Epub 2021 Feb 25.
The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a destructive crop pest native to North, Central, and South America that recently has spread to Africa and Asia. Isolates of Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) have the potential to be developed as low-risk biopesticides for management of fall armyworm, and a commercially available formulation has been developed for control of fall armyworm in North and South America. In this study, the virulence (LC and LT) of several SfMNPV isolates towards larvae of both corn-strain and rice-strain fall armyworm was assessed. Bioassays with corn-strain larvae revealed that the isolates could be organized into fast-killing (LT < 56 h post-infection) and slow-killing (LT > 68 h post-infection) groups. Rice-strain larvae exhibited narrower ranges of susceptibility to baculovirus infection and of survival times in bioassays with different isolates. Two SfMNPV isolates with rapid speeds of kill (SfMNPV-459 from Colombia and SfMNPV-1197 from Georgia, USA) along with an isolate that killed corn-strain at relatively low concentrations (SfMNPV-281 from Georgia) were selected for the complete determination of their genome sequences. The SfMNPV-1197 genome sequence shared high sequence identity with genomes of a Nicaraguan isolate, while SfMNPV-281 formed a separate clade with a USA and a Brazilian isolate in phylogenetic trees. The SfMNPV-459 sequence was more divergent with the lowest genome sequence identities in pairwise alignments with other sequenced SfMNPV genomes, and was not grouped reliably with either the 1197 clade or the 281 clade. SfMNPV-459 contained homologs of two ORFs that were unique to another Colombian isolate, but these isolates were not placed in the same clade in phylogenetic trees. This study identifies isolates with superior properties for control of fall armyworm and adds to our knowledge of the genetics of SfMNPV.
草地贪夜蛾，即草地贪夜蛾（J.E. Smith）（鳞翅目：夜蛾科），是一种原产于北美洲、中美洲和南美洲的毁灭性农作物害虫，最近已传播到非洲和亚洲。草地贪夜蛾多核多角体病毒（SfMNPV）的分离株有潜力被开发为用于防治草地贪夜蛾的低风险生物农药，并且已经开发出一种商业制剂用于在北美洲和南美洲防治草地贪夜蛾。在本研究中，评估了几种SfMNPV分离株对玉米品系和水稻品系草地贪夜蛾幼虫的毒力（LC和LT）。对玉米品系幼虫的生物测定表明，这些分离株可分为快速致死组（感染后LT<56小时）和缓慢致死组（感染后LT>68小时）。在使用不同分离株的生物测定中，水稻品系幼虫对杆状病毒感染的敏感性范围和存活时间范围较窄。选择了两种具有快速致死速度的SfMNPV分离株（来自哥伦比亚的SfMNPV-459和来自美国佐治亚州的SfMNPV-1197）以及一种在相对低浓度下能杀死玉米品系的分离株（来自佐治亚州的SfMNPV-281）来完全测定它们的基因组序列。SfMNPV-1197基因组序列与尼加拉瓜分离株的基因组具有高度序列同一性，而SfMNPV-281在系统发育树中与美国和巴西的分离株形成一个单独的分支。SfMNPV-459序列在与其他已测序的SfMNPV基因组的两两比对中具有最低的基因组序列同一性，差异更大，并且在系统发育树上与1197分支或281分支都没有可靠地聚类。SfMNPV-459包含另外一个哥伦比亚分离株特有的两个开放阅读框的同源物，但这些分离株在系统发育树中没有被置于同一分支。本研究鉴定出了对草地贪夜蛾具有优异防治特性的分离株，并增加了我们对SfMNPV遗传学的了解。
