Whole genome comparisons reveal panmixia among fall armyworm (Spodoptera frugiperda) from diverse locations

Abstract

The fall armyworm (Spodoptera frugiperda (J.E. Smith)) is a highly polyphagous agricultural pest with long-distance migratory behavior threatening food security worldwide. This pest has a host range of >80 plant species, but two host strains are recognized based on their association with corn (C-strain) or rice and smaller grasses (R-strain). In this study, the population structure and genetic diversity in 55 S. frugiperda samples from Argentina, Brazil, Kenya, Puerto Rico and the United States (USA) were surveyed to further our understanding of whole genome nuclear diversity. Comparisons at the genomic level suggest panmixia in this population, other than a minor reduction in gene flow between the two overwintering populations in the continental USA that also corresponded to genetically distinct host strains. Two maternal lines were detected from analysis of mitochondrial genomes. We found members from the Eastern Hemisphere interspersed within both continental USA overwintering subpopulations, suggesting multiple individuals were likely introduced to Africa. Comparisons between laboratory-reared and field collected S. frugiperda support similar genomic diversity, validating the experimental use of laboratory strains. Our research is the largest diverse collection of United States S. frugiperda whole genome sequences characterized to date, covering eight continental states and a USA territory (Puerto Rico). The genomic resources presented provide foundational information to understand gene flow at the whole genome level among S. frugiperda populations.

Resistance bioassays and allele characterisation inform analysis ofSpodoptera frugiperda(Lepidoptera: Noctuidae) introduction pathways in Asia and Australia

“…Taken as a whole, similar bioassay results between native (i.e., Brazil, USA) and various invasive populations suggested potential significant genetic diversity in introduced populations. This concurs with population genomic analyses (Tay et al 2020, Zhang et al 2020, Schlum et al 2021 Australian (chlorantraniliprole, indoxacarb; this study) populations were unlikely considering the short time frame since the very recent arrival of FAW especially assuming a west-to-east spread (Goergen et al 2016, Cock et al 2017, Nagoshi et al 2018, Nagoshi et al 2019b). Another explanation for the differential responses of the two Australian populations that we studied is that they have different fitness because of variation in genetic diversity which reflects the number of individuals founding the populations.…”

Geographic Monitoring of Insecticide Resistance Mutations in Native and Invasive Populations of the Fall Armyworm

“…Field-evolved resistance to Bt insecticide in the FAW has been reported from Puerto Rico [ 12 , 13 ], Brazil [ 14 , 15 ], Argentina [ 16 ], and the USA [ 17 ]. Five mutations causing Bt resistance have been reported.…”

Large Genomic Deletion Linked To Field-Evolved Resistance To Cry1F Corn In Fall Armyworm (Spodoptera Frugiperda) From Florida

“…Taken together, currently available data support that while there is gene ow between S. frugiperda from the Caribbean and continental USA 19,31 , practical resistance to Cry1F in North America emerged locally and not as a result of migratory dispersal. Our current hypothesis is that resistant alleles affecting SfABCC2, the only relevant Cry1F resistance marker identi ed so far, are maintained at high relative frequency in S. frugiperda populations.…”

“…The genomic DNA from a pool of three larvae from the FL39 population identi ed as belonging to the corn host strain was previously sequenced on an Illumina HiSeqX device running a 2x150bp paired-end con guration, as reported elsewhere 31 . The raw data were processed to remove low quality bases using the CLC Genomics Workbench v 20.0.4 (Qiagen, Aarhus, Denmark) trim function using default parameters before analysis.…”

“…The collected specimens were visually inspected and identi ed as S. frugiperda by morphology 36,37 and stored at -20°C until required for analysis. When needed, we refer to samples using a naming protocol described previously 31 , which includes the rst three letters (USA) representing the country of origin, the next two letters representing the rst two letters of the state of origin (AL for Alabama, GA for Georgia, FL for Florida, SC for South Carolina, TN for Tennessee), and a number differentiating samples from the same location.…”