Submitted to: Molecular Ecology Notes
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/20/2007
Publication Date: 5/11/2007
Citation: Perera, O.P., Blanco C.A., SchefflerB.E., and Abel C.A. 2007. Characteristics of 13 ploymorphic microsatellite makers in the corn earworm, Helicovepa zea (Lepidoptera: Noctuidae). Mol. Ecol. Notes. doi: 10.1111/j.147-8286.2007.01806.x Interpretive Summary: Helicoverpa zea (Corn earworm or bollworm) is an important pest of over 30 different crops, including cotton and corn. As a pest species with a potential to develop resistance to transgenic crops as well as other insecticides, understanding the genetic make up of natural populations of this pest is a very important step in developing successful resistance management programs. Population genetic data are scarce for this species due to the difficulties encountered in isolating suitable genetic markers in the past. Here, we have successfully employed an enrichment protocol to isolate genetic markers and have characterized 13 markers sufficiently variable to study natural populations of this insect species. In addition to population genetic studies, these markers will be extremely useful for developing genetic maps to study inheritance of genes responsible for insecticidal resistance. Keywords: genetic markers, microsatellite, SSR, Helicovepa zea, bollworm, Lepidoptera
Technical Abstract: Corn earworm, Helicovepa zea, is an important pest of cotton in the United States. Lack of suitable genetic markers have hindered population genetic studies of this species. Although a number of simple sequence repeat (SSR or microsatellite) markers developed for other species had been evaluated on this species, no SSR markers suitable for population studies had been developed for this species. Partial genomic libraries of H. zea enriched for simple sequence repeats were screened to identify polymorphic marker loci. Twenty two microsatellite loci were tested and thirteen polymorphic loci producing single signal peaks were selected for use in population genetic studies. Insects collected from field locations near Stoneville, MS, were used to test the suitability of these markers for large scale population studies. The number of alleles per locus ranged from 2 to 9 with an average value of 4.46 while the effective number of alleles per locus ranged from 1.07 to 2.45 with an average of 1.81. Observed hererozygosity (HO) ranged from 0.0422 (locus HzMS3-4) to 0.542 (locus HzMS3-41). Gene diversity (HE) values ranged from 0.068 (Locus HzMS3-4) to 0.595 (Locus HzMS4-23) with a population average of 0.372. Probability tests indicated that the population was deviated from Hardy-Weinberg equilibrium (HWE) due to significant heterozygote deficiencies at the loci HzMS1-6, HzMS4-14, and HzMS4-16. Heterozygote deficiency may be a result of the presence of null alleles at these three loci. No significant genotypic disequilibrium was detected between any pair of loci.