Population variation of Spodoptera frugiperda (J. E. Smith) in the Western Hemisphere

Spodoptera frugiperda (J.E. Smith), the fall armyworm (FAW) is the most economically important maize pest in the western hemisphere. It has been hypothesized that two specific host strains exist for FAW: a host strain that feeds on rice, known as the rice host strain; and a host strain that feeds primarily on maize, known as the maize host strain. Recent studies have confirmed that the dividing line between the two host strains is not clear cut and that adults from the maize host strain will mate with adults from the rice host strain under certain circumstances. My dissertation research focused on the genetic variability of the maize host strain because there is a lack of information in this area of FAW research. Amplified fragment length polymorphism (AFLP) was used to assess the genetic variability of twenty populations from the maize host strain. The populations were from Mexico, the continental United States, Puerto Rico, Brazil, and Argentina. Three FAW outliers were incorporated into the study as controls, collected from Royal Paulonia, lemon tree, and bermudagrass. Additionally, another species of armyworm, the beet armyworm, Spodoptera exigua (Hubner) was also used as an outlier. The objective of this research was to evaluate whether the majority of genetic variability was within populations or between populations. The AFLP results showed that the majority of the genetic variability is within populations and not between populations, suggesting that FAW in the Western Hemisphere are a major population.