Genetic Characterization of Fall Armyworm (Lepidoptera: Noctuidae) Host Strains in Argentina

Abstract

Fall armyworm is a major economic pest throughout the Western Hemisphere. Previous studies of populations in the southern United States, Brazil, and the Caribbean demonstrated the existence of two morphologically identical but genetically distinct host strains that can only be distinguished using genetic markers, including polymorphisms in the mitochondrial Cytochrome Oxidase I (COI) gene and in the Z-chromosome linked Triose phosphate isomerase (Tpi) gene. The strains differ in some physiological and behavioral characteristics, most notably their preference for different plant hosts, but are capable of hybridizing in the laboratory and in the field. These traits suggest that the strains are in the process of divergence, which may or may not be hemispheric in scope. The objective of this study was to determine whether the two strains are present in Argentina. It was found that the strain-diagnostic haplotypes of the COI and Tpi genes subdivided the Argentina population into two major groups. Each group displayed biases in their distribution among different host plants that were generally consistent with expected strain behavior. The overall results indicated that Argentina fall armyworm exhibit similar genetics and behavior to populations in the rest of the hemisphere. In addition, the Argentina populations had comparable haplotype frequencies to those from Brazil and Texas, consistent with possible interactions with these fall armyworm groups, but appeared to have had minimal exchanges with those from Puerto Rico or Florida.

Inferring the annual migration patterns of fall armyworm (Lepidoptera: Noctuidae) in the United States from mitochondrial haplotypes

“…The CS-h1 and CS-h3 haplotypes were generally infrequent, averaging 10% and 1% of the population, respectively (Table 2). Similar haplotype proportions have been observed in surveys of fall armyworm populations from Puerto Rico to South America (Nagoshi et al 2007, 2010, 2012). …”

Host Association of Spodoptera frugiperda (Lepidoptera: Noctuidae) Corn and Rice Strains in Argentina, Brazil, and Paraguay

“…This may be another explanation for the occurrence of both mitochondrial haplotypes, that is, maybe they differ in their migration patterns or the preference of haplotype to different host plants may be inßuenced by environmental and seasonal factors exhibiting differences in the availability of alternative host plants as was determined by other studies (Prowell Pashley et al 2004;Nagoshi et al 2006aNagoshi et al , 2007aMachado et al 2008;Vé lez Arango et al 2008). Interestingly, however, the Buenos Aires population from corn Þelds analyzed by Nagoshi et al (2012) may be hybrids, because it was typiÞed as rice haplotype with the mitochondrial COI marker, but as corn haplotype by its nuclear TPI gene sequence.…”

Spodoptera frugiperda (Lepidoptera: Noctuidae) host-plant variants: two host strains or two distinct species?

“…Because of the latter it is possible to highlight the fact that both variants occur in sympatry (Pashley 1986 ; Pair et al 1986 ; Machado et al 2008 ). The FAW is also an excellent migrator with two putative migration patterns (Nagoshi et al 2012a ), one going from South America to Texas and the second going from the Caribbean to Florida, as inferred from the fact that individuals from South America (Argentina and Brazil) share comparable haplotype frequencies with those collected in Texas as do Caribbean and Florida populations (Nagoshi et al 2012b ). These results suggest that the two strains may occur in sympatry throughout the Americas and the Caribbean.…”