Combining Tpi and CO1 genetic markers to discriminate invasive Helicoverpa armigera from local Helicoverpa zea (Lepidoptera:Noctuidae) populations in the southeastern United States

Authors: Nagoshi, Rodney; GILLIGAN, TODD - Animal And Plant Health Inspection Service (APHIS); BRAMBILA, JULIETA - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2016
Publication Date: 8/21/2016
Citation: Nagoshi, R.N., Gilligan, T.D., Brambila, J. 2016. Combining Tpi and CO1 genetic markers to discriminate invasive Helicoverpa armigera from local Helicoverpa zea (Lepidoptera:Noctuidae) populations in the southeastern United States. Journal of Economic Entomology. 109(5):2115-2124.
DOI: https://doi.org/10.1093/jee/tow177

Interpretive Summary: The Old World bollworm is an imminent invasive species that presents a significant and serious threat to U.S. agriculture. This moth has been established in Brazil, Paraguay and Argentina and reported in the Caribbean islands. Introduction of this pest into the Western Hemisphere has already had significant economic impact where Brazilian agribusiness suffered an estimated $2 billion USD in costs to loss and control during 2014 alone. Invasion of the Old World bollworm into the U.S. will likely bring similar costs. In order to identify the Old World bollworm from the native cotton bollworm, scientists at the USDA, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, and USDA-APHIS, Gainesville, Florida, collaborated to develop genetic markers that can accurately and reliably differentiate between the invasive Old World bollworm and native moths. Using markers previously established for identifying the native cotton bollworm, similar markers were characterized in the Old World bollworm and provided an unequivocal differentiation between the two species as well as a basis for identifying individuals that were hybrids between them. These unambiguous genetic markers are critical to providing additional information to support the anatomical identification keys for distinguishing between these species. In addition, they will be essential for assessing potential migratory source populations and interspecies hybridization events so that effective control programs can be developed in advance of the impending invasion.

Technical Abstract: The recent establishment of the Old World pest Helicoverpa armigera into South America has had significant economic consequences and places the rest of the hemisphere at risk, emphasizing the need for improved methods of monitoring. A major complication is that a sibling species endemic to the New World, H. zea, is morphologically very similar, with the two species capable of producing fertile hybrids in the laboratory. If such hybridization is significant in the wild, it could impact the effectiveness of control methods for both species. The objective here is to provide new genetic resources applicable to Helicoverpa populations in northern Florida and neighboring states (a region at risk for H. armigera)that can distinguish the two species and possible hybrids. The genetic variability in segments of the mitochondrial Cytochrome oxidase 1 (CO1) and the Z-linked Triosephosphate isomerase (Tpi) genes was determined for H. zea from the southeastern U.S. These data were compared to DNA sequences from H. armigera specimens from Morocco and Australia. Phylogenetic network analysis showed a clear demarcation between the two species for all gene segments. As a test for utility, field-collected specimens that could not be distinguished by morphology were shown to be H. zea using both the CO1 and Tpi markers. These results extend earlier studies establishing CO1 as marker for discriminating the Helicoverpa species complex and introduce a new sex-linked.