ITS variation and population genetics in Helicoverpa zea from the southern USA and northeastern Mexico

The bollworm or corn earworm (Helicoverpa zea Boddie), is a major pest of cotton and corn, and causes damage to at least 30 other crop species in the USA and Mexico. It is considered a migratory species that constantly reproduces in Mexico and moves to the USA seasonally. It can be supposed that they constitute a near panmictic megapopulation in North America. To test this hypothesis, we collected larvae from different plant hosts (corn, sorghum, soybean, cotton and tomato) from the states of Veracruz, Tamaulipas, Nuevo Leon, and Coahuila (in Mexico) and from Mississippi and Texas, USA, on the same season and year. We designed primer pairs to amplify internal transcribed spacer 1 and 2 (ITS1 and ITS2). PCR amplification of corn earworm specimens with ITS1 and ITS2 primers yielded 500 bp and 750 bp amplicons, respectively. Genetic differences between geographic populations and host plant preference were examined using nucleotide diversity and genetic distance estimates. Results will be discussed.