Abstract
The beet armyworm, Spodoptera exigua, is a significant agricultural pest of numerous crops and has caused serious economic losses in China. To effectively control this pest, we analyzed its genetic variation, population genetic structure and demographic history. We used mitochondrial DNA (mtDNA) fragments of the cytochrome oxidase subunit I (COI) and eight nuclear microsatellite loci to investigate genetic diversity and population genetic structure of S. exigua populations at 14 sampling sites in western China. Both mtDNA and microsatellite data indicated low levels of genetic diversity among all populations. A moderate genetic differentiation among some S. exigua populations was detected. Neighbor-joining dendrograms, STRUCTURE, and principal coordinate analysis (PCoA) revealed two genetically distinct groups: the KEL group and the remaining population group. Isolation by distance (IBD) results showed a weak significant correlation between geographic distance and genetic differentiation. Haplotype networks, neutrality testing, and mismatch distribution analysis indicated that the beet armyworm experienced a recent rapid expansion without a recent genetic bottleneck in western China. Thus, the results of this population genetic study can help with the development of strategies for managing this highly migratory pest.
Highlights
The beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), is a significant polyphagous pest on vegetables, maize, cotton, soybeans, and ornamental plants [1,2]
All individuals of S. exigua in the 14 locations were collected by using sex pheromone traps from June to October from 2012 to 2018, including 11 populations collected in western China, 2 populations collected in Multan, Pakistan, and 1 population collected in Hanoi, Vietnam
The estimates of microsatellite genetic variation differed among these populations
Summary
The beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), is a significant polyphagous pest on vegetables, maize, cotton, soybeans, and ornamental plants [1,2]. In China, S. exigua was first recorded in Beijing in the 1890s. It has a wide distribution in the main crop-producing areas of China and has caused severe economic losses in recent years. S. exigua has spread to some provinces in North and East China and has infested a total area of over 2.7 million hectares [4]. This pest especially damages welsh onions in Northern China and has infested more than 8000 hectares in Tianjin, reducing the annual welsh onion production by 30% [5,6]
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