Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, SK CANADA.
London Research and Development Centre, Agriculture and Agri-Food Canada, London, ON CANADA.
PLoS One. 2019 Jun 27;14(6):e0218993. doi: 10.1371/journal.pone.0218993. eCollection 2019.
The bertha armyworm (BAW), Mamestra configurata, is a significant pest of canola (Brassica napus L. and B. rapa L.) in western North America that undergoes cyclical outbreaks every 6-8 years. During peak outbreaks millions of dollars are spent on insecticidal control and, even with control efforts, subsequent damage can result in losses worth millions of dollars. Despite the importance of this pest insect, information is lacking on the dispersal ability of BAW and the genetic variation of populations from across its geographic range which may underlie potential differences in their susceptibility to insecticides or pathogens. Here, we examined the genetic diversity of BAW populations during an outbreak across its geographic range in western North America. First, mitochondrial cytochrome oxidase 1 (CO1) barcode sequences were used to confirm species identification of insects captured in a network of pheromone traps across the range, followed by haplotype analyses. We then sequenced the BAW genome and used double-digest restriction site associated DNA sequencing, mapped to the genome, to identify 1000s of single nucleotide polymorphisms (SNP) markers. CO1 haplotype analysis identified 9 haplotypes distributed across 28 sample locations and three laboratory-reared colonies. Analysis of genotypic data from both the CO1 and SNP markers revealed little population structure across BAW's vast range. The CO1 haplotype pattern showed a star-like phylogeny which is often associated with species whose population abundance and range has recently expanded and combined with pheromone trap data, indicates the outbreak may have originated from a single focal point in central Saskatchewan. The relatively recent introduction of canola and rapid expansion of the canola growing region across western North America, combined with the cyclical outbreaks of BAW caused by precipitous population crashes, has likely selected for a genetically homogenous BAW population adapted to this crop.
褐带长翅卷蛾（BAW），又名麦蛾，是北美西部油菜（甘蓝型油菜和芥菜型油菜）的重要害虫，每隔 6-8 年就会周期性地爆发一次。在爆发高峰期，人们会花费数百万美元来进行虫害防治，即使采取了防治措施，随后的虫害仍可能造成数百万美元的损失。尽管这种害虫很重要，但有关其扩散能力以及其地理分布范围内种群遗传变异的信息却很缺乏，而这些信息可能是其对杀虫剂或病原体敏感性存在潜在差异的基础。在这里，我们研究了在北美西部褐带长翅卷蛾地理分布范围内爆发期间的种群遗传多样性。首先，使用线粒体细胞色素氧化酶 1（CO1）条形码序列来确认在整个范围内的信息素诱捕器网络中捕获的昆虫的物种鉴定，然后进行单倍型分析。接着，我们对褐带长翅卷蛾的基因组进行测序，并使用双酶切限制位点相关 DNA 测序，将其映射到基因组上，以鉴定出数千个单核苷酸多态性（SNP）标记。CO1 单倍型分析确定了分布在 28 个采样地点和三个实验室饲养群体中的 9 种单倍型。对 CO1 和 SNP 标记的基因型数据进行分析表明，褐带长翅卷蛾在其广阔的分布范围内几乎没有种群结构。CO1 单倍型模式呈现出一种星状的系统发育，这通常与种群数量和范围最近扩张的物种有关，同时结合信息素诱捕器数据，表明此次爆发可能起源于萨斯喀彻温省中部的一个单一焦点。油菜的相对近期引入以及北美西部油菜种植区的快速扩张，加上褐带长翅卷蛾由于种群急剧减少而周期性地爆发，这些因素可能选择了适应这种作物的遗传上同质的褐带长翅卷蛾种群。
