Observations of genetic differentiation between the fall armyworm host strains

Nagoshi, Rod

doi:10.1371/journal.pone.0277510

Cited by 5 publications

(11 citation statements)

References 63 publications

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“…Specifically, our haplotype data agrees with the hypothesis that the population that overwinters in south Texas (TX) spreads north and east to dominate the central US west of the Appalachian Mountain Range. Additionally, our data confirm that the population that overwinters in south Florida (FL), disperses north, east of the Appalachian Mountains as has been previously described (14,24,25).…”

Section: Discussionsupporting

confidence: 89%

“…The fall armyworm species is comprised of two morphologically identical but genetically distinct strains, the C-strain and the R-strain, that co-occur throughout the Americas. These strains are host associated ( 13 – 15 ) or more recently allochronic ( 16 – 18 ), referring to the two primary behavioral differences that have been observed between strains. For the purposes of this study, we will focus on the C-strain which is a primary economic pest of corn and sorghum.…”

Section: Introductionmentioning

confidence: 99%

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Revisiting fall armyworm population movement in the United States and Canada

et al. 2023

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IntroductionBiophysical approaches validated against haplotype and trap catch patterns have modeled the migratory trajectory of fall armyworms at a semi-continental scale, from their natal origins in Texas or Florida through much of the United States east of the Rocky Mountains. However, unexplained variation in the validation analysis was present, and misalignments between the simulated movement patterns of fall armyworm populations and the haplotype ratios at several locations, especially in the northeastern US and Canada, have been reported.MethodsUsing an expanded dataset extending into Canada, we assess the consistency of haplotype patterns that relate overwintered origins of fall armyworm populations to hypothesized dispersal trajectories in North America and compare the geographic distribution of these patterns with previous model projections.Results and discussionWe confirm the general accuracy of previous modeling efforts, except for late in the season where our data suggests a higher proportion of Texas populations invading the northeast, extending into eastern Canada. We delineate geographic limits to the range of both overwintering populations and show that substantial intermixing of the Texas and Florida migrants routinely occurs north of South Carolina. We discuss annual variation to these migratory trajectories and test the hypothesis that the Appalachian Mountains influence geographic patterns of haplotypes. We discuss how these results may limit gene flow between the Texas and Florida natal populations and limit the hereditary consequences of interbreeding between these populations.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Revisiting fall armyworm population movement in the United States and Canada

et al. 2023

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“…There is evidence that the differences in host specificity are determined by genes on the Zchromosome, which is supported by data showing that polymorphisms in Tpi exon sequences provide a more consistent and accurate determination of strain identity than COI [28][29][30]. In addition, the high genetic variability observed in an adjacent Tpi intron segment makes it a useful tool to compare populations, where it provided new insight into the biology of the host strains [28,31].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, polymorphisms in COI can at least partially differentiate two populations denoted as host strains that differ in their distribution on different plant types in field surveys (reviewed in [26,27]). The C-strain generally predominates in corn, sorghum, and cotton, while the R-strain can be found in all the hosts in North America (behaving as generalists in plant use) but appears to be more specifically associated with forage/ pasture grasses, turf grasses, alfalfa, and millet in South American populations [28]. The two host strains are morphologically indistinguishable but are genetically distinct, differing in their COI haplotypes as well as in other strain defining molecular markers.…”

Section: Introductionmentioning

confidence: 99%

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Using genetic comparisons of populations from Arizona, Mexico, and Texas to investigate fall armyworm migration in the American southwest

Nagoshi,

Tessnow,

Carrière

et al. 2023

PLoS ONE

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Fall armyworm (FAW) is a global agricultural pest, causing substantial economic losses in corn and many other crops. Complicating efforts to control this pest is its capacity for long distance flights, which has been described in greatest detail for the central and eastern sections of the United States. FAW infestations are also routinely found in agricultural areas in southern Arizona, which lie beyond the western limits of the mapped migratory pathways. Climate suitability analysis found that the affected Arizona locations cannot support permanent FAW populations, indicating that these FAW most likely arise from annual migrations. A better understanding of this migration would provide insights into how large moth populations can move across desert habitats as well as the degree of gene flow occurring between FAW populations across the North American continent. In this study the Arizona populations were genetically characterized and compared to a selection of permanent and migratory FAW from multiple sites in the United States and Mexico. The results are consistent with migratory contributions from permanent populations in the states of Texas (United States) and Sinaloa (Mexico), while also providing evidence of significant barriers to gene flow between populations within Mexico. An unexpected finding was that two genetically distinct FAW subpopulations known as “host strains” have a differential distribution in the southwest that may indicate significant differences in their migration behavior in this region. These findings indicate that the combination of mitochondrial and Z-linked markers have advantages in comparing FAW populations that can complement and extend the findings from other methods.

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Assessing fall armyworm (Spodoptera frugiperda) allochronic behavior as a predictor of local strain composition in United States populations

Miller,

Tessnow,

Meagher

et al. 2024

Front. Plant Sci.

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The fall armyworm, Spodoptera frugiperda (J.E. Smith), is comprised of two genetically distinct strains that are morphologically identical yet exhibit differences in their behavior and physiology (C-strain and R-strain). Evidence of ongoing genetic differentiation between strains highlights the importance of considering strain identity in research and management of fall armyworm populations, but the logistical and technical burden of genotyping limits strain-specific applications. Controlled experiments with laboratory colonies have shown that the strains engage in allochronic (“allo” – different, “chronic” – time) mating behavior, with C-strain mating early in the evening (0–5 hours after sunset) and R-strain mating late in the evening (5–10 hours after sunset). Using temporal field collections and genotype data, we show that strain-specific variation in allochronic male mating behavior occurs across Texas and Florida fall armyworm populations, both of which act as primary source populations for annual migrations of this pest into the continental United States. Time of capture in pheromone traps was significantly different between strains in both Texas and Florida, with the R-strain males consistently being collected in the traps late in the night. The C-strain males were generally captured earlier in the night than their R-strain counterparts, though there was notable variation in the timing between nights and across locations. Allochronic behavior in field populations is consistent with previous laboratory studies reporting differences in the timing of mating between the strains, however increased variability in behavior within and across native populations was observed. Although allochronic behavior in local populations may partially contribute to reproductive isolation between the strains, the behavior is not consistent enough to serve as a complete reproductive barrier. Furthermore, the observed variability in behavior both within and between independent sampling events, especially in the C-strain, poses a challenge to the development of models that utilize time of capture as a predictive phenotype for monitoring strain identity in local populations.

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Observations of genetic differentiation between the fall armyworm host strains

Cited by 5 publications

References 63 publications

Revisiting fall armyworm population movement in the United States and Canada

Revisiting fall armyworm population movement in the United States and Canada

Using genetic comparisons of populations from Arizona, Mexico, and Texas to investigate fall armyworm migration in the American southwest

Assessing fall armyworm (Spodoptera frugiperda) allochronic behavior as a predictor of local strain composition in United States populations

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