ARS | Publication request: First microsatellites from Spodoptera frugiperda (Lepidoptera: Noctuidae) and their potential use for population genetics

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2011
Publication Date: May 16, 2011
Citation: Arias, R.S., Blanco, C.A., Portilla, M., Snodgrass, G.L., Scheffler, B.E. 2011. First microsatellites from Spodoptera frugiperda (Lepidoptera: Noctuidae) and their potential use for population genetics. Annals of the Entomological Society of America. 104(3):576-587.

Interpretive Summary: Fall army worm (Spodoptera frugiperda) is an important insect pest of corn, though it affects many other crops such as cotton and soybean. This insect is normally controlled by pesticides and to a less extent with a toxin from the bacterium Bacillus thuringiensis (Bt). At least two strains of this insect are recognized based on their behavior, since no morphological differences can be distinguished. Given that some populations of this insect have shown resistance to Bt toxin, that this insect can migrate or be transported by weather conditions, and that different strains cannot be distinguished based on morphology, the only tool to identify and monitor strains is by molecular methods. For that purpose, microsatellites are a suitable and powerful molecular tool for identification. We have developed 178 of those microsatellites for fall army worm, and these allowed accurate identification of each of the eight colonies tested. No other microsatellite had been reported for this particular insect before, thus, our work will provide a very useful tool for the identification, monitoring and analysis of the genetic variability of this insect.

Technical Abstract: This is the first report of sequence-specific microsatellite markers (SSRs) of Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), an economically important pest of the American continent. We developed 178 microsatellite markers using pyrosequencing, and screened 15 individuals from 8 isofamilies collected from three geographical areas, Puerto Rico (PR), Texas (TX) and Mississippi (MS), including Bacillus thuringiensis (Berliner) (Bacillales: Bacillaceae) resistant and susceptible colonies. Cluster analysis was performed to determine the potential use of these SSRs in discriminating populations. SSR polymorphism grouped individuals of each colony together with a reliability of 100% estimated by bootstrap. In this analysis, colonies from TX grouped away from those from PR, but the two MS isofamilies grouped with TX and PR separately. Genetic distance between individuals of the same isofamily ranged between 0.22 and 0.56, whereas minimum genetic distance between isofamilies was 0.83. Unique pattern informative combination (UPIC) scores were calculated, and the 80 SSR markers that had UPIC scores of =1 are listed according to their discriminating potential. UPIC scores allow reducing costs by choosing fewer and highly informative markers for future studies. Heterozygosity of S. frugiperda individuals, estimated as the percentage of multiallelic loci based on 120 SSR markers, ranged between 35 and 59 %, with a difference of 2-15% between individuals of the same geographic region. The markers reported will significantly enrich the pool of molecular markers available for S. frugiperda. In addition, they could be used for monitoring migration of populations, in the development of biocontrol agents and for management practices in general.